Is that just because no one cares to create a TAS for the game? I don't know anyway a RTA would be faster than TAS other than no good TAS exists.
I’d say more like the TAS is outdated, a person can discover something new that the person doing the TAS didn’t.
Usually the timing rules aren't the same for TAS and RTA, as TAS timing always starts at console power-on while RTA usually when 'new game' is selected from the menu.