Dear Neville
What you said is interesting. Parsley in Hebrew is Petrozilia פטרוזיליה
The Aruch Hashulchan writes that karpas is petrozilia, “ואין אנו יודעים מה זה”
Possibly Rav Ganzfried had it in Hungary and Rav Epstein did not have it (or even knew what it was) in Lithuania.