BoGT Goku vs BoGT Gohan

[Captain Cadaver]

There's no implication given up to that point that Goku had any gains in power. I wish it could be explained as such, bit its just a :toei ism

Because Goku just powered up against him, the implication of the show is that Goku never really powered up against anyone else beforehand. Even Ledgic, even though it makes no sense.

That's a pretty big contradiction right there. If Goku needed to go SSJ against Redjic rather than use more of his base power and his later base power was shown to be superior to that previous data as well as superior to someone far above Redjic or Lood, that proves Goku did grow in power between the start of GT and the events on M2. Far better to think so rather than handwave it as a Toei inconsistency when it needn't be.