The only vessels Nomads can fly are Nomad ships. Otherwise, you're not Nomads. I sincerely doubt this is backed by Aoi as a form of "breakoff Wild" type of faction. Nomads are limited to Nomad ships. Nomad ships mean you're a Nomad, and thus any other non-nomad related character can attack you at will. (With prerequisite engagements lines.)
Do not attempt to tell the community what is or isn't metagaming. That interpretation is up to the staff. If you feel an instance has occured, report it to the staff and let the report run it's course.