I haven’t fully understood what you’re doing since you haven’t said where you are putting effects.
In my own normal setup, I’ll record a mono source to a mono track. I’ll put mono effects in the insert chain (for example, an amp sim, a compressor, maybe a limiter). The output of the mono track after the last insert goes to the stereo master bus, or perhaps to a stereo group.
I’ll use a send slot for stereo effects, such as reverb, chorus, delays.
I guess I’ll have to try what you’re suggesting and see if I can duplicate the concern, but I have in the past played around with stereo inserts on a mono track, and I recall that as long as I sent the output to a stereo master bus, it worked fine. But since I don’t normally put a stereo effect in an insert slot, I could be wrong.