[Freeswitch-users] Why only 3 frame sizes in mod_opus?

I think that only 3 frame sizes (10ms, 20ms and 40ms) are implemented in mod_opus? Is there a reason for not adding the entire list of 2.5, 5, 10, 20, 40, and 60 ms (https://tools.ietf.org/html/rfc6716#section-2.1.4)? Thanks