I have already answered above: Goku got stronger because he trained. Freeza learning to mantain his power output. Freeza is, thus, stronger than before. This Freeza wouldn't have lost against SSB Goku from ROF, hence this Freeza is clearly a "stronger" fighter. I don't understand what is hard to grasp about such an elementary explanation. In the context of the episode no one talks about a "power level" increase, it's something you are deducing but that still appears improbable for other factors.
You keep arguing that your argument is in the sake of simplicity, and yet it's based on anything but a simple premise: Freeza increasing his power in a way we've never know it was possible, that the episode doesn't even remotely address.
I believe I have also already addressed your point about the mastered Super Saiyan.
No, it's not ever mentioned they got a "stronger" Super Saiyan through meditation in the way you're intending it (if it was your point, I'm honestly having a hard time following your claims), just a more efficient one. This is common knowledge (in fact I'm fairly surprised it's been brought up here); you'd do well to read one of the many threads on the argument if it's still unclear to you. It's also never stated that meditating gave them a result similar to physical types of training. Just that they could reach, again, a serene mindset which made them capable of using their Super Saiyan for extended periods of time. The purely power-related aspect clearly appear to be something they gained from training in the ROSAT.
Gohan got strong enough to have power rivaling his father in a day of training after regaining Ultimate, as explicitly said by the narrator as footage of him taking on SSB Goku was played during this statement. The context, based on this narration and footage used, is that Gohan did indeed get strong enough to rival Goku in SSB.
I don't understand how this is supposed to be related to the matter of proving meditation can increase one's own ki, but it's also debatable since Gohan already doesn't "rival" his father in the purest sense. At bare minum, a fully powered Goku can take Gohan down with ease; so the narrator is referring to some other form of Goku which could realistically be something even below SSB. I have Gohan in-between Super Saiyan 2 and Super Saiyan 3 Goku, for one, and I certainly don't feel like I'm not giving Gohan's justice.
Other than jumping to conclusions, I'd say you'd do well to take the narration in Super with an added grain of salt. Or according to you, is Roshi is stronger than the likes of Goten and Trunks, or even Super Saiyan 3 Gotenks? Because the team was said to be comprised of the "strongest" fighters in the universe... which is most likely not referring to sheer strength, but only because they're the most suitable for that kind of battle.
Extra context. Goku shudders when Freeza displays his Golden Evolution's energy control and goes on a spree of murder, when he didn't do so when he first fought Golden Freeza.
This also happens immediately after Freeza's speech has revelead he can mantain his form as long as he wants, which may just be enough to make Goku feel unconfortable.
Either Goku's wrong, or he's right. There are no ifs, ands, or buts about it. Unless him or someone else points out he was wrong like during the Buu Saga, I'm inclined to believe him.
That's kinda the idea since
nobody here, most certainly not me, is arguing he's wrong or that we don't have to agree with him. This is clearly a matter of different and possibly feasible ways in which we're reconciling what was said by Goku; given what we've been told before in the same episode and the entire series, one conclusion is, however, simply far-fetched compared to the other.
