Probably 3rd party clients that offer quality of life / usability improvements over the website.
E.g. I use Hackers [1][2] because it is much easier to read stories on mobile and supports dark mode. Unfortunately, it doesn't support commenting or downvoting (yet?)
Nothing about timekeeping is simple, with or without this change. Not only do some regions already not observe DST (even within the same state/region); some switch to/from DST at different times of year (and this date changes from year to year).
For a timekeeping library (which likely uses a system-level source of data / the IANA tz database) this shouldn't have any effect.
Good point about a signature not hiding the data. I got my terminology mixed up. I thought it was encoding it in a way so that only the payment processor could see.
But that's not necessarily the case either, as somebody else brought up the fact that identifiers ARE in fact passed to the merchant.
I believe while the token is generated once, each transaction is signed with a unique signature (I believe that's the term) that only the payment processor can decipher. The merchant doesn't get any stable/identifiable information that can be used to track you across purchases/sessions/stores.