My issue with holsters like this are the lack of good retention, compared to the nice "click" of a quality kydex holster, as well as the lack of a rigid trigger guard (not sure if that is the right term), which could create a situation where material or a finger gets onto the trigger when you don't want it to, creating an environment for a ND, especially if you are carrying a striker fired or really any firearm in condition 0.
If the desire is for appendix IWB carry, why not just get a high quality kydex holster designed specifically for that?