Hey Tonquin!
Every time I take my alchimist from cap back to lvl 1 (doing back to back ETR + RTR), I have problems with my known spells list (which at cap is full, i.e. I know all the spells): while it is WAI that the list is not reset on an ETR, meaning that when I go to 32 to 20 I keep knowing all the spells, I think this should not be the case when I RTR down from 20 to 1 right after that.
However, what happens is that once I do my RTR and I start my new life taking the first level again as an alchy, in the spell selection panel I cannot pick any spell. What I assume is going on, is that the game thinks I already (still?) know all of them, and hence I have nothing left to pick. Luckily I always have enough banked gems to get (at least) to lvl 2 right away, and when I take the second level this bug is gone and I can again select spells to learn from the full list; however, if I had no banked gems, I'd have to lvl from 1 to 2 potentially without any spells, since I could not select any at the start of the new life.
Now, I know that one could go right away to Jorasco and get from vendor scrolls for almost all alchy spells to inscribe them (which is what I usually do, just at lvl 2 rather than at lvl 1), but a new player might not know this, and would most likely have no banked gems to get to lvl 2 and "avoid" the problem of going through the first step of this new life with no spells. Nevertheless, I'm pretty sure this is not WAI.
IIRC, I used to have the same issue with artificers - hence I assume it's a common problem to all classes where one can inscribe spells (hence wizards might suffer the same). Doing some archeology on the old forums it looked like this was indeed a known bug for wizards some 10 years ago...