There are different variants for the MB818, as there are for the PLS8.
Those are clearly listed with band specifications on the Broadmobi website.
So yes, Purism will have to offer different variants of that one as well.
The MB818 is not suitable for the US market and doesn’t support the basic bands available there; it is largely a variant for China Mobile specifically, though it could be used partially on Verizon (but not Sprint, AT&T or T-Mobile).
The MB818-A1 is one variant for the North-American market (AT&T, Verizon, Sprint) and the MB818-T1 is a variant for another part of North America and other markets such as Australia and some Asian countries (those where the US had some influence and US standards apply).
The MB818-E1 is the variant for Europe, Africa and most other countries (those without US standards and excluding China).