If not for the GT Perfect Files, I think everyone would agree that GT Gohan is nothing special. The writers even discussed having an episode where Gohan regains his fighting senses, but it never came to be.
However, I saw a pretty interesting video recently about Gohan having his “Ultimate” eyes in GT and it brought me back to the idea of this Gohan indeed being Ultimate.
Anyway I think the writers at least saw GT Gohan as at least way above his start of Boo Saga self. Vegeta says he’s dragging Goten and Trunks instead of Gohan because they need to train, and Base Gohan > SSJ Trunks makes him a beast.
I think maybe Gohan was close to getting his SSJ back in BoGT.
I have Goku SSJ3 (BoGT) a little stronger than Gohan Base (BoGT) and the latter slightly stronger than Ultimate Gohan (Arc Boo).
I have a theory, but I see little possible, is that Goku's SSJ3 multiplier was recently nerfed on Planet M2. In that case, you could have Goku SSJ3 (BoGT) > Gohan SSJ (BoGT).
I think CC had a theory that Gohan only re-unlocked SSJ when Goku was out in space too, and that Goku wasn’t surprised because he thought it was thanks to Baby’s power up.