Most people here are crazy, you crazy, crazy people. Piccolo stomps Vegeta's ass into smithereens.
He outperformed even MSSJ Goku, while he was tired. Goku didn't fall below base Vegeta as he could even keep an aura up
The idea that the Cell Juniors went easier on Piccolo is also kinda... handwaving the implications just like you say it's handwaved later on the Boo arc. Cell's main intention is making Gohan suffer... he knows Gohan and Piccolo share a bond, assumedly... would the Cell Junior go easier on Piccolo and on Piccolo alone? Not killing is one thing, because they didn't want to kill, they wanted to torture so Gohan could snap...but that's different from leaving the fighter standing up and in good conditions, if they had the power to put Piccolo down, he'd be eating dirty like the Earthlings... they don't need to kill him, but they must make it as most painful for Gohan as possible.
Gohan wants to win. Piccolo knows he has no chance of winning if they fight in SSJ. Knowing Piccolo, do you think he'd be "woww they won't fight in SSJ, I can win then!!!". No, because Piccolo isn't like that, he knows under normal circumstances he is outmatched and won't celebrate a win in which he knows the other fighter couldn't use his true power. He's like Vegeta on this matter, like when Vegeta was in pain Goku held back SSJ3 on him. Gohan knows Piccolo well. Vegeta likely does too, and even if he thought Piccolo would go for the W on him if they were pitied together, he'd give two fucks and turn into a SSJ. He wouldn't care about the media if Piccolo wanted to KO him. Maybe he could even plot an strategy of turning SSJ so fast for the human eyes to see and KO Piccolo quickly, using it in a very quick burst. Moreover, there's no guarantee who he will face first. The odds of him facing Piccolo first is low. And he took Goku first. He defeats Goku (in his head) and then done, tournament lost all meaning to him. So it's very easy to explain all of this, even more with Gohan knowing Piccolo's mentality and knowing he isn't there to win and isn't there for the money like 18. With 18 tho, then yeah, he has to be prepared for her to use FP.