imho srm have never been that good at giving clear/detailed info
the srm website says...
The LOOK carbon crank arm weighs 127 grams including Trilobe pedal inserts. The aluminium version comes with more cost effective and durable aluminium arms, 170 grams, also designed by SRM.
srm shop says...
PowerMeter weight: 640 grams with carbon cranks, 53/39 chainrings, 133mm spindle and axle screws
640g for a standard pm seems good, logically the axle is 24mm, and you're stuck with shimano rings (barring the x1 option which seems to have a different body design though maybe it's just cosmetic difference?)
against a 'standard' shimano srm there's some weight saving, plus the trilobe cranks, and for those who are willing to buy extra axles (somehow) and chainrings there's the ability to move to different frames, though i'd think that's a limited market, and they don't say if it would affect calibration swapping all the bits
going after the largest market with shimano probably makes sense, but if you don't want shimano then tough
imho it's just a lighter shimano srm with trilobe cranks to avoid the need to stock different crank lengths, unless/until they give some other options all the 'modular' claims are just marketing bs