To be clear, I fully do believe and expect that the actual number of aircraft around the TW ADIZ is probably more than they have detected and reported. How much more and often that is the case, I have no opinion on.
However in this specific case, my overall point is that the idea of the ROC military being able to detect four J-15s flying in the eastern side of the ADIZ is a very reasonable idea, and there's no reason for us to assume that they were flying at low altitude as default, as your post on last page #3000 did.
That doesn't exclude the possibility that there may have been additional J-15s which they didn't detect or didn't report on this occasion or on past occasions, but to answer nelBi's question, this does appear to be the first time (that I can recall) that J-15s have been reported from ROC MND ADIZ maps, and certainly from that vector.