The key feature of an OWB concealment holster is the trailing belt loop. The loop that is behind the trigger guard.
It is found on the pancake design as seen in this Simply Rugged Cuda
https://www.simplyrugged.com/ecommer...407&parent=669
Also used in the other most common concealment holster, the Nelson #1 Professional, example the Milt Sparks 55BN
https://www.miltsparks.com/outside-the-waistband/55-bn/
Without the trailing loop on an OWB holster, there is nothing to pull the grip into the body.
Another consideration is cant. A canted holster, with the muzzle rear, often called FBI cant, will rotate the gun a bit and also aid concealment. Another consideration is a straight drop holster could probably allow the gun to be drawn by somebody behind you, but a canted holster, with the muzzle facing rear, would be very difficult for somebody behind you to draw from your holster, unless they were significantly taller than you.
Some new to concealed carry will gravitate to a holster like the Blade-Tech Classic (
https://blade-tech.com/products/clas...=6067188498460 ) or a BlackHawk SERPA (
https://www.blackhawk.com/holsters/s...ster/1580.html ) because they are well known products and, especially the SERPA, are often one of the few holsters available at the big box or gun store. While each have their good points, the Blade-Tech for range/training/competition and the SERPA perhaps for field use while boating or ATVing, neither are very good concealment holsters.