On all but the top tier MBPs, USB C ports on Macs have different specs for data transfer (often the ones on the right of the machine will have half the transfer speed).
As far as I can tell, every single Apple Silicon MBP has all ports at full speed. The early Apple Silicon Mac Minis (M1, M2) also had this arrangement. However, as noted elsewhere, this has changed (they now have 3 Thunderbolt ports and 2 non-Thunderbolt USB-C ports).
The Intel MBPs had more variance, but they only had the 2+2 configurations in 2016 and 2017. The 2018 and 2019 generations had all full-speed ports.
On all but the top tier MBPs, USB C ports on Macs have different specs for data transfer (often the ones on the right of the machine will have half the transfer speed).