I have a 13xx and 14xx gen 1 and had a 15xx gen 1 and they all worked / didn't with the same mags.
The issue is always the spines of some mags is thicker and doesn't fit the rear slot.
The key for true north to pull it off would be to make the mags that don't work work, and the mags that already do work not be all loosely goosey now.
I'd assume to cover variances they would be machined the same way. If gun 1 was tighter than gun 2, it would get machined slightly more to the new dimension.