Exactly - it's a screwup on Apple's part, not OpenBSD's.
> bug in the macOS firewall, packet filter (PF)
Mullvad's article lacks proper wording and shits on the wrong target.
> a bug in the macOS firewall, packet filter (PF)
> We believe the firewall bugs must be fixed by Apple.
I don't see how you can interpret that as shitting on OpenBSD.