I would say yes? They make Wordpress which is pretty open and usable by default and it is properly opensource. Since taking over Tumblr they seem to have been making reasonable improvements and in general trying to keep it open.

In general they have been favourable to open source and open standards. So when they say they are adopting an additional open standard I have high hopes.

But FWIW I also think that Threads joining the fediverse is likely a good thing. It is true that it may allow many people to be more comfortable on a user-hostile platform, but IMHO that is their right. I think the biggest concern is that if Threads or a small number of large platforms are the majority of users they can add proprietary extensions but I don't think the biggest issue. The biggest strength is making the fediverse more popular, and allowing more people to pick more open options without needing to ditch or convince their friends upfront.