Decentralised or distributed does not necessarily imply blockchain just because the blockchain has these features it could also be other things such as activitypub etc...

Or distributed hashtables.

I was slightly worried about that as well but after reading through the article it doesn't seem to be about blockchains or cryptocurrencies, although we'll have to wait until the next posts to really figure out what it's actually about.

Not necessarily a bad thing. Given Mozilla's track record, that would be a good investment opportunity.