If they wanna do both, they can. I'm just saying I don't think it's the best use of their resources because running a mastodon instance is a huge task. And companies having a Twitter profile was only necessary to get their blog posts noticed. On the fediverse, there's no reason for that extra step when you could just follow the blog directly. That's less work for the reader and less work for the poster and no extra service required.

It probably makes it more likely.

I disagree. Running an instance doesn't give you any insight into how to implement ActivityPub and anybody can study the source code without running an instance. There are quite a few orgs running instances, but, as far as I know, WordPress is the only widely known software that has actually integrated AP and they never ran their own instance.