This is exactly how me and every person in my guild is too. A lot of the time, it just so happens the most aesthetic choice for a lot of people happens to also be the top-performing covenant. Not to mention there are literal 1-case scenarios to pick each of the 4 covenants for many of the classes. So when OP refers to "top 1%" he really should specify if he's referring to top 1% of raiding, or mythic+, or PvP, or AoE, or Single Target, etc. because for Havoc DH, for example, Kryian = best Mythic+, Venthyr = best Raiding, Necrolord = best burst, Night Fae = best survability.
Ironically, and unexpectedly for me because I don't play Rogue, but I've had a few Rogue friends that were really looking forward to being Night Fae long before parses came out in beta. They just like the atmosphere of that zone and the characters.