They're totally fine because you only use the stand when the bike is stationary. That way the stand only exerts a force on the bike when its stopped and parked.
There are possible issues:
If the stand acts as a washer under the axle nut, it can possibly interfere with proper seating of the nut. Notice many nuts have a serrated or textured edge to help bite down a bit better. A hard steel washer will reduce that bite. This will permit the rear wheel axle to move causing brake/frame rub.
Rear weight - the stand adds weight behind the rear axle, so it contributes to unweighting the front and adding that weight to the rear wheel.
Trailer interference. Most trailers clamp to the rear axle somehow. A rear axle stand will interfere with any trailer clamp.
Pannier clips - your rear panniers will probably have a low clamp. The rear stand may obscure or shrink possible hooking points. On the other hand, the rear stand may offer additional new hooking points. Deploying the stand may be difficult with a left-side pannier fitted too.
There are positives. Your stand is near the panniers so it is closer to the Center of Mass when the panniers are loaded. By comparison, a BB stand is more centered on the bike.
Personally if you don't care about weight, look for a dual-leg stand. They're a lot more stable for loading the bike. Downside they're heavier, require a chainstay bridge with a mounting hole, and can interfere with the cranks or lower chain stretch.