Sorry...I'm afraid you were misinformed.
Lactic acid occurs because we are exercising at a leave where we use more oxygen than we can deliver and as a result, lactic acid cannot be cleared and you get the burning sensation that we all know and love
The only thing we can do to improve our lactic acid build up to is increase our oxygen capacity and delivery and it clears as we lower intensity and oxygen is more readily available and utilized.
Don't take my work for that - just google it.
A lot of people will believe that before accepting the truth about oxygen and it being a byproduct of oxygen debt...perhaps, just maybe... stretching and DOMS could be the same?!?
*Edit* - the advanced stretch they taught you was called proprioceptive neuromuscular facilitation (PNF) and involved working with muscle spindles to allow for more range of motion - still nothing to do with muscle repair.
*Further edit* - sorry, I obviously didn't read it thoroughly...
I'm going to be simple here;
Are you telling me, you started running and you ached, and after doing a few runs (and adding stretches) you now don't ache?