Sure is and I thank you. .....
Your "machine" stitching as well as the rest of the holster, appears to be sound.
For now, I'm throwing in with what
dahermit replied.
With time, this crack will propagate down to the bottom area and in fact, I'm surprised it isn't already there.
By the way, that is great looking holster. The crack should be an easy fix and after applying the glue, I would clamp it, firmly but not tight. I sandwich the leather between to strips bamboo or plastic. Once the clamps are in place, remove any excess cement before it dries. Currently I'm using Loctite-Stik'n seal. Forget wood glues or standard rubber cement. ....
Be Safe !!!