>>19575037See
>>19574779. Nothing in the actual text says that the Mega Charizard is his and the screenshot seems to be taken in X/Y (not to mention that it's level 100, which is way too high for a non-battle facility NPC).
The whole "Steven has a Mega Charizard X!" thing came from people looking at the scans, ignoring, noticing the Mega Charizard X screenshot near Steven and concluding it HAS to be his even though there's nothing stating that. It's made-up bullshit.