Actian/PSQL & Incremental/Differential Backups

I have a Actian (Pervasive) DB instance that we are backing up on a server. The vendor is telling us that Actian/PSQL does not support incremental or differential backups. I read some Actian docs and they are ambiguous at best and contradictory at worst but do seem to indicate that only "full" backups are recommended.

They also indicate a "backup agent" that works with many recovery products and mentions other features that would support that it does work.

If you look at the PSQL logs it shows the the DB going into freeze/thaw and a VSS writer running. We have not purchased an add-on "backup agent" from Actian.

I have a hard time believing this isn't really working. I have restored data from RR many times including full volumes but I guess some data could be corrupted. How would you ever know? How do I test this? Does anyone have any first hand experience with Actian PSQL?