@ellestad I believe the classic 7572 recipe was blended with some sheng. That's what I was told, and it certainly looked that way from separating the leaves. The last 7571 I had still had that flavor (7572 these days doesn't taste the same). There also used to be some "purple mark" variants of shu bricks (8592 is one I used to enjoy IIRC).
Yee On has a 7342H bing that captures the taste of that style of blend.
I think it's largely gone out of fashion, probably because of the price of moderately aged sheng