TBF it’s a major PITA to redo the partition table like this, if even at all possible given the extant layout. This was introduced with Nougat, though, with major chip vendors like Qualcomm ready with support in their BSPs right out of the gate back in 2016. I think eight years is enough time to let everyone get themselves up to speed.
Not just seamless, but safer updates as well. A failed boot from the newly updated partition(s) can be detected with the malfunctioning slot flagged by the lower-level bootloader, allowing for an instantaneous rollback.