Hello Gabriele,
It is quite difficult to pinpoint exactly what you talked about with the photo link. The colour was definitely very off in that picture and there is little description.
Semi black tea is a concept that we pioneered to define certain productions. It is not yet popular in the tea trade to use that term yet, though slowly people are recognising the need to do so and some selections are so labelled.
Mei Jian 梅尖 or Mei Zhan 梅占 is a cultivar broadly employed throughout Fujian in various strains and for various productions, including oolongs and black teas. Yet its productions do not resemble anything like that picture in your link.
Tanyang is very famous for its black tea, as one of the three original Minhong gongfu red teas ( i.e. black teas ). You are right that Fu’an Da Bai is a major production cultivar. It is defined as black tea and all properly produced Tanyang Gongfu are true black teas, not semi-black. Pricing is chaotic throughout China for famous labels. You have witnessed it.
