I read that part again now and there was something I missed. When 18 states that Vegeta had to be stronger, probably because of his scouter or whatever, Vegeta himself realized Cell wasn't even trying. After he matched blow for blow and Vegeta already started to lose confindence.Where? All he says is that Cell got stronger, but Vegeta is even stronger, which he's baffled by. Immediately after that Vegeta says that Cell isn't being serious and Cell agrees saying he needed the warm-up, which surprises #16.
So here we have Vegeta being perfectly able to asses the situation without having to resort to ki sensing. How come he wasn't able to sens this earlier, when Krillin and Goku can?
True, but this falls perfectly within the definition "of not overestimating" the opponent, given that both were hell bent on not allowing Cell to become stronger.Trunks and Piccolo are not about to take such huge risks obviously, but there's no indication that they figured out Cell hid greater power, like what Krillin did.
Honestly now, it all falls back to character and personality.
Consequential evidence against another set of consequetial evidence. Of course I'm not denying my bias here, nor would I continue to debate this if I were given better proof than Vegeta and Babidi said this then it must be so.Which doesn't have to mean he's wrong in this case just because some don't agree with the implications it brings.
Vegeta is only wrong, when he hasn't seen the opponents full power. If Vegeta sensed Piccolo's full power at the Cell Games, there's no reason to think he's wrong, but that's why I have my own reservations about it, because Vegeta was busy with his Cell Junior, so it would be hard to concentrate on anything else.
I have no idea how Toriyama would have done things, had he written the story differently and had Vegeta and Piccolo fight in the tournament, but I can't imagine him not being able to take on a base Saiyan when he fought and surpassed the SSJ before.