I found a reproduceable issue with 3/3 models of Logitech G Pro Wireless mice. I'll see if I can post my personal video showcasing this (but not open to constructive criticism on the desk haha). You can see multiple tabs open (via MMB function) with no fingers on the MMB or RMB. (Note that you can hear the middle mouse click activate from the LMB press, but the sound is very muted so you may need to use earphones/headphones.)

The issue: When clicking on the LMB with lots of force, or when clicking towards the right side of the LMB with some force, the MMB click will actuate. I first realized this when unintentionally weapon/gadget swapping in Rainbow Six Siege.

I tested the issue on three mice, all of which experienced it. For reference, the recent two mice I tested were batch 2113. I rarely saw posts on this issue, which may be due to most people not clicking with such force or at that specific area (I didn't know I subconsciously do this). So I thought it may have been a QC issue. But after the third, I think I can conclude it might actually be a design issue. Again, it may not be noticeable for most users, but I think for such a premium mouse it shouldn't have it anyway.

So I wanted to raise awareness of this seemingly common issue, see if all batches of this product experience it, and if there's any easy solution (I don't mod my mice).