As this is explaining a possible bug, I didn’t find the form relevant.
Breeding higher Gene Strength doesn’t seem to work. I believe I’m at a slight standstill at 22 as I’m outclassed in Gene Strength. I was rollin’ through it until gene strength started to come into play.
Breeding 2 normal monsters does make a +2. But breeding 2 +2s, even if they’re quite close to my level (they were over 2/3 of it) still only makes a +2 monster.
It’s worth noting that is specifically states in the library that breeding two monsters will have the new one with a higher gene strength, when this does not seem the case.