I don’t think the FKT quilt makes that much sense for a typical FKT.
With a typical FKT you are moving fast/hard and thus staying warm and needing little in the way of insulation while moving. I’ve never needed upper body insulation warmer than a 100wt fleece anytime I’ve done anything resembling an FKT. Anything warmer is difficult to use outside of the winter. So I don’t think an FKT is a circumstance where you can really take advantage of clothing insulation to reduce insulation in the sleeping bag/quilt.
Also with an FKT you are trying to move as fast and light as possible and have probably selected a pretty good weather window so I think down makes a lot more sense than synthetic (ethics aside). It’s going to be lighter and pack smaller. I’ve never had trouble keeping a down quilt dry and don’t see FKTs as a time where that would change.
Thirdly, the optional poncho head hole seems of little use if you’re really attempting an FKT. If you have enough upper body insulation that you can opt for a reduction in your quilt, then you shouldn’t need to also be wearing the quilt while moving. Obviously one can imagine exceptional circumstances where this is needed (e.g. sick or hut) but for the most part it seems of little value. One could make the argument this is handy while breaking camp, but if you’re on an FKT this shouldn’t be more than a few minutes and I think it makes more sense to get your stuff packed away and tough it out until you’re warmed up.
I’m not saying its a bad product, just that a simple down quilt with adequate insulation seems like a better choice for most people attempting FKTs. One can get a 40-50F down quilt for 10-12oz (e.g. EE Enigma) which is substantially lighter and smaller. There are niche circumstances where synthetic, unequal insulation and head holes are benefits but 90% of the time a simple down quilt is the better option.
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