Yes, but it’s still mapped correctly, the way the graph looks is somewhat misleading.
Get a grey ramp (e.g. from darktable's filmic FAQ - #29 by kofa), adjust exposure, place a colour picker on mid-grey, adjust filmic: you’ll see that mid-grey is not changed.
You can make it ‘linear’ (actually, logarithmic, if I understand correctly) by tweaking the shoulder/toe on the advanced tab (try all options soft, hard and safe).
Here is an old preset, you may have to tweak if for the current version of filmic: