Which conda environments can be `--stack`ed upon and which cannot?

Here is my logic:

when you conda actiave --stack ..., the only thing that is left over from the stacked-upon environment is its entry in PATH.

Therefore, if a conda environment can function normally with only it’s entry in PATH, then it doesn’t necesarily need to be activate’d, I can just add it to path myself:

export PATH=<conda-env-prefix>:$PATH

Is this true?

The question then is how do I determine which conda environments need to be activated and which can just be added to path?

My theory is that if the binaries in a given environment depend on python, then they shouldn’t be stacked upon. CONDA_PYTHON_EXE changes, which python changes, import’s from the stacked upon environment wouldn’t work. Anything else is fair game.

Is this true?

I suppose the obvious answer is that they’re all different, and one would have to test the entire functionality of an environment in order to find out. I’m hoping there’s a simpler answer.