That's speculation. What we see is that Gohan couldn't react in time after being hit with that Kiai, and that's all we need to glean from the scene. The blast moved slowly enough that Satan had time to shoot at it, so if Gohan was unable to intercept it it must be due to the stun damage from the...
GT did have a TV special, it's called A Hero's Legacy. It's ass though unlike the Z TV specials.
Considering it's Super I would have zero expectations of a special for it being good. But it'd be funny to see a shitstorm brewing up after it breaks a bunch of overanalyzing fans' headcanons...
Calling him quite a master is strange too when in his previous form he called base Gotenks a weakling. Guess he now knows the difference between Saiyan's and Earthlings due to Piccolo's brains.
It's strange because he talks down Goku in the same breath and also considered Piccolos power puny and only worth absorbing for his brains lol. Just AT being stupid by that point due to burnout similar to him forgetting Gohan never died before the Boo arc.
All Gogeta confirmed was that his power was greater than just two powers being added, and Whis (who's the only character about as knowledgeable as Old Kai) never mentioned the rivalry boost.
Since new material seems to try to equalize Gogeta and Vegetto as much as they can, I'd tentatively...
Rose probably has a stamina issue like Blue, since they're counterparts. Black presumably doesn't know how to go down to the SSJG form or something, or wouldn't be able to switch forms rapidly like Vegeta did.
Perfected Blue is far stronger than burst blue, Merged Zamasu while toying was able to move faster than either the SSJGs could see and knock them straight out of God in one attack (showing he was on a different tier from Rose Black, to the point that Blue bursts would be ineffective as Vegeta...
It happened when Videl was a kid, seeing as she won the junior division. The Daizenshuu timeline puts the 24th, which Satan won, as happening in the 7 yr time skip between the Cell and Boo sagas, and before he revived the TB he was merely the world wrestling champ