I know that meats come out tender when using the pressure cooker. But that's usually when the liquid level is covering the meat.

What if I wanted to just steam the meat -- use a low level of liquid; the meat is on something that's raised above the liquid level. Will the meat come out tender in this case as well?

I have some spare rib nuggets (coated in some seasoning) that I want to steam only, not immerse in liquid, but want them to come out tender.

My wife did exactly what you're talking about with some ribs and they came out great.
She's cooked quite a few things in the pressure cooker since she got it a couple months ago and everything has been good.

Pressure cookers are fantastic to use for all types of cooking. The one thing I learned many years ago is you need to keep the contents elevated above the bottom if you are using a small amount of liquid. Once upon a time, some cookers came with a trivet and divider pots for cooking things separate. If you don't have a trivet then an easy fix is to use a collapsible stainless steamer basket with legs for standoff, the kind you can use with different pot sizes on the stove top. They are very inexpensive and can be found often in thrift stores.