I haven't ever seen a controller that does the BPSK modulation required for A ports. I suspect the standard was defined, but everyone just decided to do signalling over the CC pins on USB-C and ignore the USB-A standard.

If you know of any controllers that implement the spec, I'm very interested in knowing part numbers! If for no other reason than as a historical curiosity.

You aren't going to get 20W of fast phone charging power out of USB 2; you get 2.5W tops. USB 3 gets you to about 5W.

Meanwhile USB C goes up to 240W. You're probably never going to get that directly out of a motherboard.