This is a great question.
I have answered the question of mold errors before - see this thread: https://forum.antiquebottles-glass.com/discussion/comment/4044#Comment_4044
I could add that there perhaps is something to make of such variants, depending on the bottle, or the company in general. If you can put together a good grouping from a particular company with different molds and mold errors, then you have something. Write an article, become the expert. Collector Rick Ciralli deserves a lot of credit for taking this idea and running with it, specifically with Dr. Townsend Sarsaparilla and GW Merchant bottles. We as collectors know a lot more about these two particular companies thanks to Rick, AND...he definitely increased the interest (and to some extent the value) along the way.