Yes, this is a male Red-flanked Bluetails. First-winter males are very similar to females, and this may be partly why you are seeing more female-types.
It is good to know that you are managing to see some interesting birds at Mount Davis. HK Island does not have enough observer coverage I think. This has improved this winter with the series of good birds at Lung Fu Shan, but there is a lot of good habitat on the island, and many birds must still be overlooked.