It does matter, because the store page isn't just for buying - it's also for seeing system requirements, reading any applicable EULAs before purchase, and reading reviews. You can't do those from any other page on Steam.
Since the bundle is a separate purchase option and not replacing the option to buy TTD on its own, it also allows people to easily find out what they're in for by providing a description of what OpenTTD is, as opposed to just buying TTD on its own.
https://store.steampowered.com/bundle/70574/Transport_Tycoon...
But the OpenTTD item listed in the bundle is non-existent at the moment.