Form endpoints for each Eloqua tracking domain

Hey,

I have a question regarding the way you can select a tracking domain endpoint on Eloqua forms:

My assumption was always that if a HTML form was posting into Eloqua, then the tracking domain that the form posts into should match the one that the front-end form is sitting on.

However, recently I noticed that there doesn't seem to be any impact on tracking or visitor profile to contact linkage if a different domain is used (as far as I can see).

Is this the case? If not, what are the benefits to using a form action that matches the tracking domain?