I think DBS has Goku tell Beerus he can't go any higher than SSJ3 in their first fight, so Daima having Goku keep SSJ4 seems to very clearly show a contradiction and probably a different timeline.
The only people who think it was retconned are those who don't like the implications of such a strong base Goku and Vegeta against other scenes like Goku vs Great Saiyaman Gohan and the Trio De Dangers vs Goku, Gohan, and Buu. It just means some scenes are just odd but in the face of the direct...
I think the context is he didn't know Goku could counter the Galick Gun with a similar move or at least that he didn't think Goku could match its power. He saw Goku do a small Kamehameha against Nappa so it's a bit odd that he'd be surprised in any case, probably Toriyama forgetting again.
That could just mean it operates similar as an energy bullet technique, as well as it could eventually be the same as a kamehameha in power such as in Super where it appeared equal in application.
Why should Kamehameha equal Galick Gun though? Goku was using Kaio-Ken x3 to counter the Galick Gun. I tried using a theory for Kai-Ken and Kamehameha stacking together but ultimately it makes more sense that Kaio-Ken overwrites Kamehameha.
beginning of Z shows us base Goku's full power at 416...
Some Gods of Destruction may be in Blue Goku's tier or once we're in that tier before. Belmod's quote looks like he's not familiar with concentrated ki amplification attacks.
The article mixes anime and manga sources as well as guides for anime and manga separately without treating them as evidence for anime and manga as separate entities. It treats all evidence as universally applicable to both the anime and manga. They need to treat anime and manga as separate...
Maybe the speed of Freeza flying toward the blast made the kick stronger than if he kicked it while stationary. Like they might think he couldn't kick it back while stationary but underestimated his run-up kick power.
Scotty told you everything you need to know. Although I haven't heard that lost the film masters. Even if they did, FujiTV would have high quality tapes in storage, but due to how the laws work in Japan, Toei would have to pay to use them for a home release. So that's never going to happen.