As the statute makes no provision for nationwide service of process, Due Process requires that the statutory joinder of out of state parties to a statutory collective action prove sufficient minimum contacts of the original deft within each forum state of the out of state parties.
DISSENT
The addition of new plaintiffs doesn't change the singularity of the lawsuit, within which the court has already acquired its specific jurisdiction. Alternatively, the deft's conduct towards the out of state plaintiffs relates to its conduct within the original forum state.
As it's a national statute, interests of particular states aren't implicated in the same way.
The statute's designation of added plaintiffs as parties is merely to distinguish their status from that of representatives without a personal interest.
https://www.opn.ca6.uscourts.gov/opinions.pdf/21a0186p-06.pdf