If they have their own Plat card then they would be able to come in with you either way and sit at the table with you.
I'm not sure I get your point regarding being counted as a guest even if they have their own card because the point of eliminating guests is that the primary shouldn't be able to bring in additional (i.e. even more) people who don't have their own Plat card at all.
I for one, do agree that eliminating the 2 guest policy will ease crowding. If 5 primary people come in instead of 15 (or 30 instead of 90 etc), it definitely makes a big difference.