He didn't do a visible power up and his eyes didn't turn focused until he decided to go full power, definitely a much lower percentage than that 50% display.
Cell only absorbed 15,000 people which is less than a tenth of what he absorbed after Gingertown lol. I don't think he powered up massively from it, in fact he didn't even have an aura when he fought Piccolo.
Until it's confirmed he got rusty like Moria I think it's just a small possibility. Crocodile seems to have some of Roshi's plot-oids going on so his power seems to change with his mindset
In Japanese it uses the same or similar Kanji to Ultra Instinct, but Vegeta interpreted it as maximizing his will to fight rather than letting go of inhibitions and letting the body move on its own like UI. Guess that's why the English translation used "ego," which sort of fits with Vegeta's...
The full color manga draws a distinction between the Saiyan and Freeza sagas, I think the main reason it's not as popular as the other three post-23rd is because Vegeta became an anti-hero and then a genuine ally of Galu, plus it was revealed that Freeza was behind the Saiyans' destruction and...
I think the excess amount of Bruits waves are just required to make a tailless Saiyan an Oozaru/GO. If he went past his limit it'd have been stated, it was stated Galu reached his full power by sucking the other Saiyans' peen energy after all.