Says the person who discounts clear evidence from the actual original manga (the actual panels) in favour of a statement in ANOTHER ANIME scene created 20 years later. Besides as I said in that cover scene base Gohan was present too. So base Gohan=Piccolo=SSJ1 Goku by your (erroneous) logic.
Because there isn't clear evidence in the original manga. Most all of your evidence is based on your own interpretations on where you think that characters should be strength wise, while ignoring what is actually shown. Simple fact of the matter is though is that Piccolo is shown sparring with Ssj Goku, thus gains that he would gain as a Super Saiya-jin would be proportionally smaller in his base, and that Piccolo is established later to have a battle power high enough that he could be considered strong for not being a Super Saiya-jin.
Another baseless assumption as Goku was clearly surprised that someone else managed to become a Super Saiyan.
He was surprised by this random new person who neither he nor anyone else had met, was somehow a Super Saiya-jin. There's no reason to assume that Goku would be shocked if Vegeta became one.
No. It was explicitly stated that Mecha Freeza was stronger than he used to be and he was clearly trying his best to beat Trunks. Even if he was only at 50% of his maximum the ease with which Trunks defeated him compared to how SSJ1 Goku fared against 50% Freeza is enough to conclude that SSJ Trunks was stronger than SSJ1 Goku was on Namek. Also Goku commented that he didn't know whether himself could beat them as fast as Trunks did and he said so having their full power in mind. Of course later it is proved that SSJ Goku and SSJ Trunks were on par but the point is that the are both stronger than SSJ1 Goku used to be on Namek. Additionally Goku learned to master the SSJ form - don't think he trained to do so? Also don't you think he received a Zenkai boost from his battle with Freeza? Besides it is common sense - Wikipedia page here.
1) It's established by Gohan that Freeza wasn't at anywhere near his full power (in relation to Namek) when he came to Earth, and no indication is given at all to indicate that he powered up at all from that level.
2) Since when is a single ki blast (the only thing Freeza did to Trunks) suddenly an indicator that he was "clearly trying his best" to beat Trunks? He fired the single ki blast, without any indication that he suddenly jumped or spiked his battle power at all, and then thought he beat Trunks. That's it.
3) How was it proven at all that Trunks and Goku were on par with one another? Literally nothing is mentioned or even hinted at that they were on equal grounds. Their little sword/finger exchange is irrelevant given that neither were trying, and nothing was mentioned after that point.
4) Goku wasn't anywhere close to death following his battle with Freeza, thus he wouldn't have obtained a near-death power-up.
5) Common sense says that, when it's established that Freeza is nowhere near full power, and nothing is suggested or stated after that he raised his strength up from that point, then he wasn't at full power during his skirmish with Trunks.
Yet Dr Gero was capable to immobilise Piccolo the first time he attacked him. Besides Gero COULD measure power levels and he didn't consider Piccolo as anything special while in the city. You assume that Goku powered up to his max base for that punch while we know he had to act quickly to make Gero stop. Also given the unknown threat why Piccolo didn't increase his own power level to the maximum too if you are going to assume that Goku did so? Funny that for you only Piccolo could be suppressing his PL.
No, I don't think that it was only Piccolo that was suppressed at the time, but when Goku actively attacks Gero in a burst of anger to try and stop him from destroying the rest of the city, under the assumption that #19 and Gero were the ones that had terrorized the future and killed off everyone else (and who was touted to be stronger than Freeza), there's no reason at all that he'd hold back to try and stop him.
And again, both #19 and Gero are enemies that both Goku and Vegeta indicated they needed Super Saiya-jin to beat, but by your reasoning, neither would need it since they'd
HAVE to be stronger in their base forms than Piccolo, who was capable of easily taking on a power-boosted Gero with no difficulty whatsoever.
Base Goku = Barely make a base strength Dr. Gero stagger with a punch, with no indication or suggestion that he was holding back his punch.
Piccolo = Able to effortlessly take on and nearly defeat Dr. Gero after his strength was augmented by a ki blast from Ssj Vegeta as well as his (Piccolo) own ki.
Looking at it objectively, there's no way that Piccolo was weaker than Goku and Vegeta's base at the time.
Base Vegeta knocked Piccolo out while Piccolo was trying to attack to help Goku. Also base Vegeta did free Goku from #19. If Piccolo was anywhere near 50x base Vegeta he would have felt nothing. Or was now Piccolo supressing his power again ... while attacking (and prove my own point about base Goku attacking #20 in the city)?
