I agree with you... I should be able to get the display name (user full name), given name (first name) and surname as dynamic properties of he person who submitted the forms... and that's not what's happening and I don't know where to fix it. The example below show two entries -- one with the user full name, and one without.

Peter's shows up with his given and surname, while the second one is blank next to the email. I surmise the reason the first one has a full name is because when I created the List in Sharepoint, it was from the Excel spreadsheet created when viewing the responses after clicking on "Open in Excel" in the Form itself. That would be the original output from the Form when it as created. When a new entry is entered in Forms, the list does not update with the most recent submission, which is illustrated the second entry lacking the user's full name.
The steps you recommended I add did nothing the change the list in any discernible way. None of the dynamic content seems linked to the User's profile other than their email.
The whole point of a Flow is to not have to refresh the list every time with my spreadsheet, or for me to edit the list after a Form submission is completed. There must be something that can be done without me having to open the spreadsheet, and relink/upload it to the List in Sharepoint.