Supersonic ejection has been survived, but it is somewhat high-risk and non-enjoyable. Notable for facial blast injuries (colossal hemorrhaging) and for knees and elbows bending in the opposite direction to that usually preferred. The Russians came up with a few interesting innovations to try to improve survivability.
In this case there may have been chance benefits of 'ejection-by-disintegration' - Siebold may have been subsonic before being 'ejected' into the windblast and possibly this occurred with his back to the direction of travel.
I very much doubt Siebold 'did' much about escaping SS2. More likely 'WTF?' followed by 'I appear not to be dead, to have mislaid my vehicle, but happily still to be in possession of a parachute'. The very nature of intense chaotic events is that all manner of outcomes are possible, even those which are genuinely or apparently very improbable. In fact, 'WTF?' may have come immediately after rather than before the detailed change in situational awareness.