They likely mean any cryptocurrency. Bitcoin is simply the only type that is generally known and hence synonymous with all things crypto.

Well, in this case this was during a Q&A session, so he was likely asked about bitcoin by shareholders (it was a shareholder meeting) to get his opinion.

Plus he makes it clear in the article that he finds it distasteful "shuffling out of your extra billions of billions of dollars to somebody who just invented a new financial product out of thin air."

Which I mean, if you're somebody who has "extra billions of dollars" lying around, you might not care to shuffle it around either.

As for other billionaires, at least one is actually into bitcoin (Elon Musk).