Hey TD.
I personally don't see new language as an act of creation because languages evolve anyway. Although if God caused it to happen directly, as in the case of the tower of Babel, then you are right, it seems like another account of God causing something to occur which would be incompatible with a day of rest.
What I find frustrating is how rest is interpreted. You mention resting from creating things is a way various groups interpret a Sabbath, yet as Diogenesister pointed out, gathering sticks hardly qualifies as creating anything.
On the surface it seems that humans are being held to a higher standard than God when it comes to observing a rest day.