Hi LEM,
The old thinking was that engine start was aborted if there was no oil pressure indication by light up. That part of the procedure still remains.
Previous thinking was to never operate an engine in ANY manner without oil pressure (one that I happily accepted). Current thinking is that the 'blow out' cycle is important, and, with roller bearings, little damage is likely to arise at the very low RPM. Allied with this, the torque supplied by the starter motor would in all likelyhood be insufficient to overcome excessive friction in an 'oilless environment', and would therefore be self regulating in protecting significant damage.
Personally, I don't like it too much, but there you go.
Regards,
Old Smokey