If elon really has a huge amount of BTC, he'd definitely store it in his own wallet. Elon might not support non-mainstream coins because there's a lot of altcoins in the industry right now, It'd be hard to pick one for every tweet that he makes.

But for real though, Elon really got a huge power he's holding right now - with the way he influence the market, that thing is scary and amaze me at the same time. The incredible thing was that Telsa didn't even make a grand announcement about their BTC investments, In its annual report, Tesla said it updated its investment policy in January so it could have "more flexibility to further diversify and maximize returns" on any extra cash it was sitting on, eagle-eyed investors managed to see that.