I am surprised your review made no mention of the fact that either the 14 or the 16 can be specced exactly the same other than size with a price difference of $200 and the differing battery capacities. Otherwise the machines can be specced the same. You instead talked about the big price disparity between the two configurations you picked and how the 14" is "almost as good" as the 16". The 14 can be specced up all the way to the 16 (other than battery size) while the 16" an be specced all the way down to the lowest 14" spec...
I am not surprised that the SD card is not UHS-iii or SD Express simply because there are no cameras using them - and for the foreseeable future. T
USH-ii is backward compatible with all previous SD cards but USH-iii is not backward compatible with USH-ii. It goes back to UHS-i speeds if a USH-ii card is inserted.
Given that high end cameras Sony/Canon etc have standardised on USH-ii, it makes sense for Apple to keep that specification.
SD Express sounds good in theory but CF express is already here and provides very high speeds.
Sony's A1 has a handy combined UHS-ii/CF type A card slot but Canon etc use CF Express Type B for high capacity and higher speeds including support for 8k raw internal recording. There is only one SD Express card available and it is half the speed of most CF Express Type B cards. Lexar have announced that they will produce a SD Express card but only in 2022. Highly likely that no UHS-iii cards will be released.
Frankly, the SD card specification names are a mess for any normal user to understand which one would suit their needs.