I disagree.
It is my guess that they spend a considerable amount of time on the freebsd distributions and generally get it right the first time.
Just off the top of my head (I haven't upgraded to 7.5, but these issues existed all the way through version 7.1 that I am currently running):
- Plesk installed perl modules in the wrong location sometimes.
- Plesk didn't try to install needed perl modules for BU to work properly
- Plesk didn't install MANY perl modules that would have made SpamAssassin more effective.
- Backup tools just didn't work "out of the box", and needed a lot of tweaking to work properly.
- The "Dr Web" Antivirus solution is horrible, and destroyed a LOT of my mail (I didn't notice it right away, because it was only mail with attachments that was being destroyed) before I disabled it and bought a 3rd party product that worked like a charm. Unfortunately, there's apparently STILL no official way to permanently disable Dr Web, so if I'm not careful and perform an upgrade, or reboot the machine, it re-enables Dr Web again. Nice.
Also, by the time they have released the freebsd dist, they have fixed the known bugs which occur in the other releases.
- Plesk still referred to FreeBSD as "Linux 4.9" in the updater.
- The updater just doesn't work
- Plesk is usually anywhere from 6 months to a year or more behind the current version of FreeBSD.
I'm not going to spend more time thinking of other things that were broken when I installed Plesk on FreeBSD, because it's not productive. I agree that Plesk is better than CPanel in many ways, even on FreeBSD - but I don't agree that they put the expected amount of testing into a product that we pay hundreds of dollars to buy. I'm not trying to be overly harsh here, but I disagree with the statement that Plesk on FreeBSD is a well-tested product.