Stephen, we need more info. (If you were female, i would say, "need more info Steph-a-nie." [old movie reference, childhood favorite]).
Like what layers you were using, how often you opened up, etc. I think as long as one can fully unzip a garment, that can compensate quite a bit for reduced breathability of the fabric.
But, having just used an old, beater thrift store nylon shell at 24 or so degrees to 33 or so degrees, and with a breathabilty rating i would subjectively rate at least twice as breathable as the older Houdini, i would say there can be a big difference when everything is closed up.
I was wearing this in combo with a homemade sleeveless powerdry high efficiency baselayer (so the fabric was advertised on ebay as) shirt i made, with a Pat 4 Cap hoody on top, and a thin 55% merino 45% nylon top on top of that. So i had 3 layers total on my arms, and i could definitely feel the wind and cold at times on my arms at least (and i run warm). It was an easy hike with not much elevation gain or loss, so i was sweating a bit but not doing a lot of intense exertion.
But it worked (very) well for my core, and didn't have to unzip all the way because the material was quite breathable. If i had worn my 2012 Houdini, i'm fairly certain i would have had to fully open up during any higher exertion periods. Granted, if i had brought the Houdini, i probably could have taken off the Merino-synth shirt, or the sleeveless MYOG PPHE shirt and been fine, but i was looking to boost my sleep insulation a little extra too so didn't mind the weights of either of those (which are both in the 4 point oz range).
Anyways, kind of a pointless post on my part, as obviously it worked for you with the conditions and approach you used. There are times when i like the convenience of not having to constantly adjust my system though, but that's just laziness on my part.
It would be interesting to try the new Houdini with a thin, dwr treated fuzzy fleece one side and smooth other, to replicate Paramo type WPB system. Seems like the new Houdini might be just right for that kind of use.