Conda installs conda packages and conda uses pip to install pip packages. However a pip package can be converted to a conda package, and then in that case the dependency will be installed by conda and not pip.
You’re correct, Conda does not call pip when it installs packages. But pip does have a subtle involvement here: Many Python packages available to Conda are packaged based on installations made by pip, and (IMO lazily and incorrectly) inherits a lot of pip characteristics. This makes the packages “appear” to be installed by pip, and sometimes induce interpolation inconsistencies.
Conda installs conda packages and conda uses pip to install pip packages. However a pip package can be converted to a conda package, and then in that case the dependency will be installed by conda and not pip.