J23,
CD is providing very good guidance.
If your son has a DIII offering a paid visit, with current economics and budget cutbacks, that is a very strong sign of their interest. Most DIII's don't do that, even if they could afford it.
DIII coaches who want your son to attend will interact in the ways your son is experiencing.
They will want an unofficial visit to meet the team, see the school, attend classes, watch practice or games, and get a complete feel of what the school and team have to offer.
Some may even go further and describe where they see your son in their program, describe the opportunities that exist for your son, describe the growth potential and even talk about Summer league opportunities.
Yes, DIII coaches are very upfront if they want your son. They will make it very clear.