The 77W that flies BOS-CDG has 381 seats
The 772 that flies BOS-CDG has 316 seats, and the A332 has 208 seats.
There definitely seems to be a decrease in capacity (even in S16 DL flew a 764 and now fly a 763). I've never flown this route in the summer, but I'm wondering if it commands the capacity and premium that a 772+332 bring.
Maybe it's because of Norwegian, or maybe AF wants to wait a bit to finalize a third flight -- if they ever do.