In Multiplayer, since 1.8 all tracks&cars will have the most recent BoP applied, without the ability to go back to previous years.Currently in ACC, performance of cars are related to a chosen year (2018,2019,2020) or a chosen serie (GT challenge, british GT). These series can be simplified into a 2021 BOP.
And when you choose the 'BOP' (year or serie), it is automatically linked to a resurfaced track if any.
So, I think that each year should be present, to reflect each BOP within the track name.
But to avoid too much modifications, perhaps that previous state could be left as is (track with 2018/2019 status) because there is no way to differentiate previous records and to sort them correctly.
You know, even Kunos doesn't know how to handle all these differences and the leaderboard in game doesn't contain year anymore
Let's go simple by adding year to US tracks.
So this is only relevant for single player. And also there, the BoP is specific to each season and track. And because there never was a different season on the US tracks, the BoP will always be the current one, even if you select a 2018 season in single player.