Just made a little test: turns out you can post a thread from #Lemmy UI to #Kbin magazine! So if you have a Lemmy account, you don't miss out on Threads creation, while having no Kbin account at all. One exception is if you want to post something more sophisticated than just a link or an article: if you're gonna add tags and other things that Kbin does over basics. š¤·
But you cannot post into Microblog from Lemmy, so keep that in mind.
From the perspective of Lemmy, community page is showing both Threads and Microblog posts in one place. It truncates microblog text to 200 characters to put in the title, putting entirety of the text behind a click.