Really just the same data you cited – the observation that channels tend to gravitate towards one preference or the other.
In my experience, it is sometimes a source of ongoing tension when the collective preference has to be continually reasserted by existing members “please use threads!” or “please don’t use threads!” (often without the “please” part).
That observation led to the idea that it may be better to encode that preference more explicitly.
That said, the idea of supporting both was considered at the time and put on the back shelf as something that may be revisited later.
I have occasionally wanted it myself, but until now, I haven’t heard any request for it.