Miles & More (Lufthansa, Austrian, Swiss, and other partners) - flexible fly smart award at Quick Check In Desk

Last Sunday I was on an LH fly smart award etix DUS - LHR. Got to the airport about 90 min before scheduled departure. Upon CheckIn at the Quick CheckIn Desk I was asked whether I wanted to check in for the originally booked flight or for an earlier/later flight - different LH flight numbers and times of departure were shown.
It even stated "award ticket flexible".

Did this happen to anyone of you?

given the fact that fly smart awards are generally non-rebookable, could this be an offer of LH to rebook because the flight was heavily overbooked (I asked the lounge warden about that)?

Normally when you book the award (on-line anyway) you have a choice of ticket. E.g., LHR-MUC would be 18000 non flexible or 28000 flexible. You obviously chose the latter option.

I never heard about that...

Maybe a new feature?

Usually awards (but not fly smart) are flexible; but there is a fee/miles cost for every change...

If this is a new feature I think it's a very good one. But will they later charge something for a 'rebooking'?