Glad someone else mentioned the Montane dyno / dynamo (older version) as I've had the original version (the Dynamo) in Montane's own, specified fabric for probably over 10 years now and replaced it with the pertex equilibrium version as it only cost me £32.50 (the dyno). No hood on either
I bought the first one as I wanted a softshell but I was not that up on gear back then so I gambled and got the cheaper, thinner dynamo. It was to replace my old sprayway banshee. This was in a windbloc membrane fabric but cold as the thick insulation layer was outside the membrane with only a thin microfleece inner to keep you warm. Very nice jacket for winter but not in wind as the warmth was so low. Anyway the dynamo was just as warm in winter if there was wind about.
Since then the newer dyno version has a more hardface to it (not true hardface tech though) making it tough. As a "98% windproof" jacket (more like about 80% in stronger wind) it works by reducing the wind through it but allowing some to get in to take away any moisture. That is in mild breeze to moderately strong winds. Above a certain wind speed it needs another, more windproof layer I'd say.
I found with my dyno that it is great if you are moving and working hard as it handles sweat well. Rain not so but I did once wear my old dynamo in 2hours plus of heavy rain when I left my windshirt and waterproof at home!!!! I didn't get cold and although wet through was actually quite comfortable. When the rain stopped my wicking base layers and the even more wicking dynamo softshell meant I dried quickly.
Anyway, I used my dynamo and later dyno all year round only I changed my layers around underneath it according to the season. I found it very adaptable and it worked for me very well for probably 8 years until I got a VR for winter. The dyno is still my spring to autumn top though.
With this in mind the offwidth jacket IMHO seems to be pretty much the same garment but by a different brand and with similar fabric. With this in mind I'd say with a bit of playing around with your layers you could use this in the hills all year round. It should breathe well under a hardshell too!! Membrane jackets would work less well under a hardshell. I'd expect it to wick and breathe exceptionally well, more like a microfleece would. My dynamo and dyno actually wicked better than my base layers which are all good brands. I know this because on a dry day when working hard the dyno would be dry on the inside as would the base layer but damp on the outside. Occasionally I have been sweating so much that the base layer was wet inside but the dyno wasn't.
BTW I nearly got one from ruck+run. They were selling them off for very cheap prices I though. Won't tell you how much as it was a pressie. I didn't because MHW is a brand that doesn't fit my shape. Although it was described as athletic which usually means slim I don't trust that brand's descriptions. I find they are more boxy cut than athletic in the past with their other "athletic" fit jackets. Since I'm tall and relatively slim the montanes and rabs fit me better.
So my advice is to give it a go on the hills as it will work if given the right combination of other layers. Like everything you have to test it out to find its strengths and weaknesses then account for them.
I think you'll find that its at least pretty close windproof in practice, deals with showers etc very nicely and adds a touch of warmth simply through the non trivial thickness of the material. 
