That is kinda true - here's what he said on Twitter:
"It takes roughly four hours per episode editing #AlphaSapphire, which is not feasible while also writing a walkthrough + doing other stuff. Based on comments, my YouTube subs prefer funny commentary & more Let's Play style videos rather than waiting for in-depth walkthrough vids. Both styles are totally acceptable; I decided to try a more professional video series, and it was not as well received, hence its removal. I will likely continue to work on the #AlphaSapphire video series exclusively for my website, as that's who it was intended for anyway."
When he did his White 2 and X Adventures in late 2012 and 2013 respectively, he went through them very quickly because he wanted to get coverage out as soon as he could. It wasn't the same case for Alpha Sapphire, possibly hence why he tried to get "more professional". He still has the written walkthrough on his site, but that's only up to the third badge at the moment.