I'm a bit unclear on the question and answers.
To me, recording a solo vocal in stereo would mean using two mics (or a stereo mic, which is effectively two mics in one case) in some sort of arrangement (X-Y, M-S, baffled omnis, ORTF, whatever), with one panned hard left and one panned hard right (matrixed, in the case of M-S). The direct sound from a voice emanates from what is, for practical purposes (assuming it's a normal voice, and not a Tuvan throat singer or something) a point source. Thus there shouldn't really be any stereo information in the direct sound. So it would seem to me that the purpose of stereo micing would be to capture the room sound in stereo, which would mean backing the mic well away, and would only make sense if the room sound were worth capturing in the first place.
Different things (which I wouldn't really call "stereo" recording) might be double-tracking a vocal (i.e. recording two separate performances of the same material - which I would usually pan to the same place) or applying some stereo signal processing to a vocal track (like delay or reverb - which would, basically, be capturing the sound of an artificial room in stereo).