I'm a regular economy-class MAN-LHR routepass user. The booking class is Y, and is fully flexible.

I usually post the miles to my LH M&M account, and they accrue at the "full" rate

Lastly, note there is a routepass promo on until the end of March. 800 diamond club points per routepass bought. I've already earned 2400 pts this way, and hope to get a couple more routepasses bought before the promo ends.