You are talking of yet another issue which is real and is related to the way TCP detects a congestion, but this is not specific to Wi-Fi. There are also problems of interoperability between TCP/IP and the Wi-Fi MAC layer, some of them could trigger congestion algorithms, but as the MCDU gets larger and larger this should not be a problem nowadays. Indeed it is a bit strange to have MCDU that are 64k large and IP packets that are 1.5k large.

What I discussed was the way the buffers are in series inside the OS, this is known since a long time. A modern operating system throughput could be 5 to 9 faster than Linux: https://www.usenix.org/node/186147