The tag alias #46259 inbetweening -> motion_tweening has been rejected.

Reason: The tags betweening, in_betweening, inbetweening, and motion_tweening all refer to the same concept.

EDIT: The tag alias inbetweening -> motion_tweening (forum #289662) has been rejected by @bitWolfy.

A reliable source (tm) has stated that inbetweening and motion tweening are different things: forum #279750.
Coincidentally, the inbetweening tag seems to be misused a lot. Mainly for things stuck in-between.