A lot of the information about that is 5 years old and hence of questionable applicability today i.e. out-of-date. I don’t think it really matters whether it is called “Fir” or “L5v2”. The key point is that Fir should have “updated specifications”, quoting JCS, as compared with the 5 earlier batches. Hence @spacemanspiffy’s question (beat me to it).
There has, over the 5 years, been a lot of chatter about future improved CPUs from NXP. The i.MX9 series now exists and uses a smaller process (hence should be more energy-efficient, ceteris paribus) but whether it is a drop-in replacement or even suitable I don’t know. Existing discussion: New NXP i.MX 9 Chips
Yes, I agree, Purism should be clear in setting expectations because otherwise we all know how that story goes.
The communication is fairly clear. The two names have been “unified”. 
They are one and the same thing.
NB: Aspen.
For many use cases, it really doesn’t matter how sexy the specifications are if you can’t use it as a, you know, phone.
Tackling this is a two-edged sword.
On the bad side … there is a lot that is simply beyond Purism’s control. They don’t make the modem and they don’t run the MNO.
On the good side … the firmware can be updated by the customer in a straightforward manner … and even a change of modem, if that became necessary, can in principle be done by the customer. The core of the phone is untouched.