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.

http://docs.actian.com/psql/psqlv12/advops/wwhelp/wwhimpl/common/html/wwhelp.htm#href=backup.09.6.html&single=true

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

http://www.pervasive.com/database/Home/Products/BackupAgent/LearnMore.aspx

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?