Form fields marked as HIDE are not sent in formdata

I was assisting a client with a form issue where some fields they pass to the form and have set to HIDE were not getting populated in the formdata object that was subsequently being sent to a workflow that is triggered on Form Submission. They have them hidden, since they are not needed by the manager, but are needed in the subsequent email.

So the following steps are done (fields are examples):

  1. Workflow triggered to get an identity and launch a form for their manager. Form is passed in userDisplayName, userDepartment, and userLocation as inputs to the form.
  2. Form sent to the Manager’s email, they click on the link and bring up the form.
  3. Form displays the userDisplayName as read-only fields marked as DISABLE and sets userDepartment, and userLocation to HIDE so the fields are there intended to pass the data through
    Reference: Documentation for Forms
  4. Manager completes 2 additional select fields, needsLaptop and needsOffice, and submits the form.
  5. The form triggers a workflow to send an email to the IT Department. The email is coming in with the userDisplayName, needLaptop and needsOffice filled out, but userDepartment and userLocation are blank/missing.
  6. When I reviewed the workflow Execution (download the CSV) I see that the formdata does not include userDepartment, or userLocation fields at all.

As a test, I had them change the fields from HIDE to DISABLE and they started working as expected.

So is it correct that fields marked HIDE, even though they are passed data or have default data set, will not populate the formdata? If it is, could that information be added to the documentation?

If that is the case, is there a way to pass data into a form and out to the resulting formdata object for the workflow without displaying it to the user on the form?