IMHO the now unavailable boomerangs have nothing to do with a change of LM's internal award space search algorithm.
Every (!) boomerang that used to been available on LM could be found in the Amadeus timetable so it was my conclusion that LM uses the Amadeus timetable for route search and then checks class availability on the segments found within that timetable.
When you now search for the same boomerangs in the Amadeus timetable, they are gone.
To verify my hypothesis, I did just a random search for "forced carrier" boomerangs within the Amadeus timetable and did found for example a C3-C2-C2.5...
... and: This boomerang still shows up in LM.
Final conclusion:
LM did not change anything within their algorithm...
BUT...
Amadeus changed it's timetable search algorithm.