Adding new entity through foreign controller with custom form input names

Correct. For the exact reason you are confirming.

That’s clear then, thanks.

No, with this I extract only the relevant fields of getData(). Since getData(‘x’, ‘y’, ‘z’) retrieves only the first argument. But this may be superfluous if the patchEntity automatically addresses the right fields, that I don’t know and is partly the reason for issuing this topic. I assumed the complete getData() as input would be troublesome as it contains form data of multiple models.

Well, I am unsure. I am quite sure it is not, respecting your experience and indication of doubt.
This is just another attempt to enable one user-facing form to possibly create entities of different models. This is one way of trying next to Nested add forms of multiple tables via form buttons - #12 by Zuluru. I figured multiple models need to be handled in one controller function/method, one way or another.