Maybe. But the consensus in-universe may be that they're generically magical runes - particularly since they do appear on soul gem rings, which, to most people's knowledge, don't have anything to do with witches. While Riona may well know better, she may still not think of them as being anything particularly specific to the "witch" state.Speaking of soul ring inscriptions, we should mention that Sabrina can read Witch Runes. That should lend some more credence to the theory that we have something to do with a Witch.
For that matter, do we know for sure that magical girls can't decode runes? If they are literally a substitution cipher for the Latin alphabet, the names on soul gems form a more than substantial enough corpus for them to have figured it out. As for guessing that it's that in the first place, it'd almost be harder not to notice that the patterns in names with repeated letters, such as "Sayaka" or "Kyoko" match.
(If it's not literally true, then that makes Sabrina's ability to read them more interesting - to us, let alone to other in-universe magical girls.