For my system, the answer is YES. But only for improved BASS.
Each of the five SX-T2N/R towers consists of the Top SX-T1/R cabinet speaker + the Bottom SX-1010N/R subwoofer.
Thus, my 2 rear towers also serve as dedicated subwoofers: RBH SX-1010N/R subwoofers x 2.
So the main reason was for having 5 identical subwoofers around the room and 5 identical speakers around the room for smooth integration.
In terms of just surround sound, I don't think having $12K/pr of speakers is necessary. But I wanted more bass around the room.
Of course, having $12K/pr surround speakers won't hurt the sound.
And, of course, I could have also used less expensive surround speakers + added subwoofers in the rears. But I wanted all 5 identical speakers (and subwoofers).