My own experience of the Uniqlo cheap-one was entirely the opposite - as someone who runs hot it feels like it regulates temperature far better than other jackets and is actually far less sweat inducing than other similar warm jackets.
I agree, I’ve got a lightweight Uniqlo I wear on dry chilly winter rides and cold commutes, find it much better than a soft shell, hardshell or anything else in terms of regulating temperature. Breezy but warm.
I like this sort of nerd stuff. Keep it up.
The number of people who need a down jacket for cycling in is extremely small anyway. You're gonna sweat in it and wreck it so, so fast.