Just to update, I've gotten back from my European tour, within which I took AF from CDG-PRG and BUD-CDG. In both directions, the BP showed "Flying Blue Elite Plus" with my DL number. The BPs both scanned for lounge access, including in a Malev-operated lounge in BUD.
I did not re-qualify for status on DL, and these flights were in March. YMMV.