.45 as a back up sidearm for Bear Hunting.
When bear hunting, are you more often on the move, or stationary in a hide?
One drawback to a drop-leg holster is that they add extra weight to one leg. They have to be adjusted and mounted and strapped in JUST RIGHT. Too loose, and your gun will move around a lot... too tight, and you'll screw circulation... too low will further encumber your movement... too high, often interferes with the family jewels.
Another drawback is that drop-leg holsters love to snag on things. As a hunter on the move, you have to deal with brush, foliage, and debris. Consider that.
To address the specific example holster that the OP posted about, consider this. If you need your sidearm while bear hunting, it's because your primary has gone down and you have seconds before you become lunch. Do you want to fumble with a buckle in order to draw your sidearm? No, you want a holster that will both carry your sidearm securely but allow for a rapid-draw.
In most cases, a good solid hip/belt holster will fill virtually everyone's needs. Drop-leg holsters are really only needed if you have to wear heavy armor - and even then, a chest rig are arguably often be a better choice. There are times when a shoulder holster or chest rig are better suited (armored tank driver).
Again, your use case will vary, depending on what your need and use will be... hence why I asked the OP that in the first place.