I’ve seen a lot of A5 Wagyu, specifically Striploin high in fat cooked very under-done.
The difference is Japanese do not eat A5 as fat steaks like Westerners do. A5 is standard cut 1/2” grilled over teppanyaki.
While Japanese Wagyu melts below body temp, I don’t believe a bleu/blue center is ideal temp - the only people eating tataki on an extra fatty cut are something you might see in a "NOBU” or other west hollywood type where you want to preserve the color and show the marbling (completely unnecessary) after it’s cooked.
Under-cooking A5 (high BMS 10+) will result in:
-More Fat globules
-thicker cut striploin is normally eaten as a steak as an A3-A4 steak.
-A5 striploin in japan is often hand sliced thin cooked medium to medium well over direct flame. Or 800F-1200F Binchotan. see>Nakahara, Jumbo, Kinrinsan, Miyoshi Kyoto, etc.
Even tenderloin, which you could argue can be on the most rare side of the spectrum is normally served medium rare.
-On fatty pigs like Mangalitsa, Iberico, the fat also melts at body temp or below. Bacon is one of the best examples where it’s high in fat, and you absolutely continue to render the fat until it’s done and the bacon is crispy.