I have played around 245 hours of breath of the wild, around 40 hours on my friends switch before I got my own and 205 hours on my own switch. I've just bought "The Master Trials" DLC for it. I've been using the heroes path and it has tracked all the way from when I started the game, to exactly where I'm standing now. I have heard that the game only tracks up to 200 hours of gameplay. If that's so, then why has it tracked to where I am currently standing if I've played 5 more hours than 200 hours? When I reach the maximum amount of trackable hours will it stop tracking me from there on, or will it remove tracked data from the start of the game?
Hero's Path Mode: This new map feature shows the path Link has walked through Hyrule from the last 200 hours of gameplay. Use the time tracker bar to see where you've spent the most time and where you have yet to explore. There's bound to be more adventures and maybe a shrine or two on the road less traveled.
This is from Nintendo's page of the DLC, which says 'the last 200 hours of gameplay'. Therefore I presume that the first 5 hours will be deleted if you go 5 hours over the limit.
This is just an alternative guess to the already existing answers:
I recently started the game and if I remember correctly it says that the 200 hours are an approximation and not an exact number. Either way, the reason might be the technical implementation of the tracker.
It could be that the tracker does not store your "GPS" location every X seconds but rather stores some additional information about your actions. It can be limited by storage space rather than actual time and the 200 hours are just something Nintendo measured as an average time it takes for a player to fill that storage.