Correct. They may not have a "FAA" freq assigned to them, such as 122.80 etc. I came from the 135 world of little airports and some fields use UNICOM as that is also the freq for their light system, etc. For those old enough, remember the FSS each state had? They had a freq as well and would "coordinate" traffic etc, albeit "advisory" only.

This is PPL 101. All of the airports we serve the jeep app plate will have a CTAF above whatever freq that airport uses and a ball note for the lighting if different then CTAF.