Glad you found a workaround, but please file a support ticket for this. If you don’t have support: (a) consider it and/or (b) send me an email with your info (contact in profile) and I’ll file a bug.
Anyway, yes. It caused us problems. Attempts to connect to machines outside of GCP would fail repeatedly due to the NA dropping the SYN. This would mean our connect() call would timeout repeatedly. There was an ICMP response I could see with tcpdump:
ICMP host aaa.bbb.ccc.ddd unreachable - admin prohibited filter, length 68