Hi Kevin,
This two species are really not so easy to separate and first winter seems to have no difference on plumage. That the reason why it is often much better to rely on voice. Maybe comments from more experienced birwatchers could be welcome to have a better opinion on this ID.
I will not affirm that it is, but your call description also match well. Also it is located to higher elevation, in Hunan (where elevation are lower than in Sichuan) it is a bird that I always find only near the top of the peak above 1800 meter, and only in dense bambou thicket.
Cheers,
Jonathan