This rather sums up why any computer with a 3.5mm stereo input needs experimenting with because it has to cope with all kinds of I out bodges. So ground to the sleeve is standard, but feeding the signal to tip, no ring or ring no tip, or tip and ring combined may all work and produce I out on one channel or both channels. For what it's worth, I discovered one of my computers needs tip and ring being commoner for a mono input, while another on the same cable has a strange hollow sound, which is because one of the channels is the opposite polarity, which results in one of the pair of audio channels it creates being inverted, which of course partially cancels in mono!
Clearly, the often quoted opinion that computer sound card inputs are generally rubbish is spot on!