@Nathan Faucett, while you are developing trust, there is no reason for it to be seen as "I don't trust you", especially if you spin it in the context of:
"hey I have have been watching you work on these and I am truly impressed with how you are handling the process. I am trying to learn and grow my knowledge and experience in the field and I could really benefit from some wisdom from people that have proven themselves in this field, like yourself. If you don't mind me asking, I am curious to know how you evaluate properties to make the decision of what is to keep as an investor vs sell?"
While empowering the wholesaler, he feels obliged to tell you and share some of what he looks for on whats a good deal vs not, especially if you praise his skills and abilities. Although he might not tell you straight up what the issue or why a particular property does not work for him, you can read through the lines as he will most likely explain in general what he looks for when evaluating what to keep vs sell. The chances of why he is letting go that property is most likely one of those reasons.