Yes. Frank doesn’t have many deep emotions, but loyalty is at the core of who he is and what he’s about.
Frank is no stranger to using people until they have nothing left to give. The vast majority of people he uses, he simply doesn’t care about what he’s asking and is banking that they will over-give.
With Doug, he holds back. He knows Doug would be really useful but doesn’t want to interfere with his getting better. Plus he also senses that Doug isn’t completely right in the head and is possibly worried that he’ll screw something up.