If you press F3 + F4 it will automatically switch to your last switched game mode, which is handy if you want to switch between two specific game modes quickly. However, if you press F3 + N it will change the last switched game mode to spectator/creative. I don't know if this is really a bug, but I think it's a bit annoying and should be handled separately.
MC-219059
F3 + N changes the "last switched" game mode from F3 + F4
Open
6
(Unassigned)
Community Consensus
Input, Player
1.16.5, 21w10a, 21w11a, 21w13a, 21w14a, 21w15a, 1.17, 1.20 Pre-release 1, 1.20.4
Retrieved
I can confirm this, but this is probably a feature request although this is actually a bit annoying.