Around 2009-2010, I built for my Alpair 10 Gen 1 a box presented as MLTL (I drew inspiration from one of Jim's publications, if I remember correctly).
Back in those days, there were already also classical bass-reflex enclosures, things called "pencils", backloaded horns etc etc.
When I look at the enclosures published nowadays for Gen 3, I see not much variation, some have increased the volume of what looks basically like a BR enclosure with the shape of a thin column, but they claim that the classical load (lesser volume, as back in 2009) is more pleasing on their favorite music etc etc. From what I(ve read so far, there are frequent claims that the 10.3 is fundamentally different from the previous versions.
So: much ado for nothing ? Maybe.
Fact is, I don't personally see a major difference in the TS parameters between 10.1 and 10.3 (Fs in the region of 36-39 hz, Qts in the region of 0,32 - 0,33...). Here is what seems to be the datasheet of 10.1:
https://www.hifi-selbstbau.de/images/stories/chassis/markaudio_MA10G/Markaudio_Alpair10.pdf
To me, it seems that any load that worked for 10.1 also works for the 10.3 and vice versa. A variation of 1 or 2 cm on the diameter or length of a vent does not say much.
As far as I know, in the speaker world, there are usually even (much) greater variations connected with manufacturing tolerances for a given model of a speaker.
What is unclear to me, on the other hand, is whether people still use a small serial LR equalizing. With the Gen 1, I remember that the vast majority of users implemented such a small equalizing circuit to compensate the baffle step effect due to the narrow front panel. With the current Alpair 10.3, most front panels are still narrow (in the 8"-9" region) but I've not seen - so far in my readings - someone using an LR compensation. I'm inclined to think that if there has been a major evolution, then it is probably in the overall balance of the FR.