“Release early, release often” attracts testers and developers alike.
If you refuse to give it a stable version number, you also refuse to promise to not reshuffle the whole software source code from one day to the next and break everything in one go.
If 0.17 is usable, they should just ship the current state as Beta 1 and then over the course of 6 months ship 3 additional Betas, 2 RCs, and then release that thing.
Then they should take 6 to 12 additional months to tighten up the loose ends and get 1.00 out of the door.
And then instead of endless release delays, they should delay features, not releases. A 6 months release cycle served both KDE and GNOME very well.