Compatibility entry for julia itself is ignored

I ran package activation and instantiation for a package that specified julia 1.5.4 in julia 1.6.0. I used the specifier julia = "~1.5.4", which I believe allows only the patch number to vary. However, there was no error or warning.

I did this:

(@v1.6) pkg> generate .julia/dev/TestPkg
  Generating  project TestPkg:

Then I touched Project.toml adding:

julia = "~1.5.4"

And then:

(@v1.6) pkg> dev TestPkg
Path `D:\.julia\dev\TestPkg` exists and looks like the correct package. Using existing path.
   Resolving package versions...
julia version requirement for package `TestPkg [5db33cc8]` not satisfied

So I did get the warning - although no error, and it did add the package to the Project.toml of the current environment.

If I understand it correctly, the [compat] section is taken into account when add-ing or develop-ing packages, not when activating project environments - there it is the Manifest.toml what is used to deal with package versions.

Right, but what if I want the compatibility checked when I activate/instantiate a project?