No; tweets have always been viewable without an account. What he did do early on was make it so you could view someone's entire profile without signing in (previously after you scrolled down a bit you'd get hit with the login flow). But then he started restricting things again; first he restricted Twitter search to logged in users, and now the entire site.

I don't know if it was requested by Musk, but the legend goes that George Hotz made the login popup dismissable in december last year.

You could always see a direct tweet without login, but his change made it possible to also see timelines or tags or use search.

Which is apparently being reverted now.