I finally found out the answer in a blue post:
It seems like the official answer is yes, with systems strikingly similar to BFA.
https://us.forums.blizzard.com/en/wow/t/pvp-rewards-and-item-levels/761970
https://us.forums.blizzard.com/en/wow/t/the-first-week-of-shadowlands-season-1/761552
These posts state that Duelist gear is equivalent to 226, and 226 is also equivalent to a +14 Keystone, thus making anyone’s experience who solely wants to pvp more difficult.
Classic TBC it is.