Not 100% sure but think the ski stuff uses same material so shouldn’t be too affected by the cold. With knees it could just be you caught it. I had a bad crash last year and was similarly grumpy until saw physio who reckoned without pads I’d have a shattered knee cap.
I find mine can be a bit stiff and rigid before I put them on if it’s cold. Once on the body heat seems to soften them up enough to shape well to my knee as normal, so assume it’s enough to make them work ok. Took a little spill in them in the cold last week but the ground was pretty soft so not a big test.
It’s in the nature of d30 materials that they soften with body heat in use and may be a bit stiff when first worn. The VPD Air is a lightweight pad. I think it sounds more like you just discovered the difference between it and the heavier duty pads. Even for a fairly low speed impact, angle is all.