Glad to hear the appearance of your vinyl was improved!
Yes, the H20 Guard & Gloss is a synthetic sealant, so it provides protection for the vinyl.
It is not really a cleaner, so even though you saw some contamination get removed from the vinyl, there is likely still some contamination left in the vinyl. Next time, I recommend that you clean the vinyl first with Revive Hand Polish, then apply the HGG for appearance and protection.
That revive says it will gloss tho, which would defeat the purpose of protecting the matte. Am I wrong?