because remember when we went from SD to SDHC - device reader needed to be compatible
No, actually when we went from SD to SDHC it also worked in Rockbox

Only the *software* needs to be compatible with SDHC, the hardware doesn't care. For a USB cardreader or similar, the software is running inside the card reader and thus you need a new reader which knows about SDHC, but for devices with native SD card controllers, the drivers can be updated to read SDHC cards without needing to change the hardware.