Officially, We switched from semver to calver:
The development versions may have 2.0.x notation, and this should be fixed for released versions.
I just tried it now, so it looks like this got addressed.
docker run -t dgraph/dgraph:master dgraph version | awk -F: '/Dgraph version/{print $2}'
v20.11.0-rc1-77-g32e48a40
docker run -t dgraph/dgraph:latest dgraph version | awk -F: '/Dgraph version/{print $2}'
v20.07.2
docker run -t dgraph/dgraph:v20.11.0-rc2-5-g2188e742c dgraph version | awk -F: '/Dgraph version/{print $2}'
v20.11.0-rc2-5-g2188e742c