The "WOUND ROLL" was failed, the MW at the end isnt a wound roll, its a separate rule.
When you need a 6+ to wound and you have re-rolls fail wounds, yes you can re-roll 's and 5's even if they can do a MW. But you dont get that MW until the end of the sequence. you cant stack MWs from wound rolls b.c it literally says "In addition to", so it has to be the final roll.