I get why he stuck with the less than inspired newer textures. From a plain old boring business perspective you want the game to look consistent with other let’s players so that their viewers won’t find your channel as jarring and make it easier for them to stick around.

Would a mix and match even work? Modern Minecraft is all soft and blurry compared to the rougher more jagged look where Notch picked a colour and hit the noise button a dozen times in gimp.