If you just read this comment chain you are replying to and the linked Reddit post, you’ll see the macOS beta has already started and are expanding currently.

Edit: according to your colleagues at least 🙏

From the Reddit post two days ago:

Starting today, we’re beginning the beta for our upcoming macOS desktop app for Proton Drive. As with the other Proton betas, we are starting with a number of Proton Lifetime accounts today, with Visionary users to be invited later.

And then a comment from proton a day later:

We’ll be expanding the beta over the next days starting with visionary users and our goal is to release it all very soon.