the whole game? that big / heavy a reset?
Having to download the whole game again isn't a requirement. It's just an update as normal. But sometimes people choose to reinstall fresh if they are having issues. I just updated my game as with other updates.
4.0.1 is now on the LIVE channel as
@ZZLEE said, but this is the set of fixes that have been playable on the HOTFIX channel. Persistence (inventory and in-game purchased, reputation, completed missions, achievements, etc.) has been the same for both LIVE and HOTFIX with the way they have been working on 4.0.1. So anything you did in either channel was available in both.
Granted it's a bit of a confusing approach for new players, but the benefit has been getting more people using the fixes but still accomplishing something in game rather than just testing as was the case with the normal Public Test Universe (PTU) eventually to LIVE approach. In those cases anything you did in PTU didn't persist or get carried over. They'll still use PTU I'm sure for very early testing, but my guess is the HOTFIX option will continue as a way to get improvements to players faster, one of their primary goals for 2025.
We are still having issues in 4.0.1 with hanger and regular elevators, which is both comical and frustrating

but I've had a couple good play sessions with 4.0.1.