It was me who complained about that. I asked iBasso for the same long press functionality when browsing by directory as when browsing by album (i.e. Play, Add to Playlist, etc.), not for Play All. My reasoning is this - if you organize your music by artist & album, and your tags aren't perfect, and you have a lot of music on the unit + SD card (which I do), there's really no easy way to quickly get to a single album and play it. Yes, you can browse to an album by directory then long press the first track and it will play beginning with that track through the rest - as long as you don't navigate away from that directory. If you do, it will stop after the currently playing track. My listening habits are almost always to play entire albums. I have several thousand albums on my player, so scrolling down the album list to get to the one I want is very painful (and, again, relies on correct tags). The basic player does have the ability to browse by artist & album, but that also relies on correct tags. Why bother putting the Directory button on the advanced player, then not give the same functionality as when using the Album button. It all boils down to ease of use. Using playlists will get the correct result, but I don't want to have to create thousands of playlists either.
I agree, it's not a show-stopper. But it sure would be nice, and would make it an easier user experience.