Disable OPEN in SharePoint Online options?

My company has a SP list for a staff directory called Who’s Who. All of the columns are visible in the All Items view except for 1 field — the Mobile Phone number. That is only visible to the HR (and IT Development) staff using a view called HR-View. I have confirmed that a general user cannot access the HR-View and that the column is not shown in Quick Edit mode.

There is 1 problem. A general user can select a person, then click on the ellipsis and choose Open. The fly-out opens and exposes the Mobile Phone number to the general users (a big no-no). Do I have to create a new fly-out for the view/edit forms, or is there a way to disable the Open menu option.

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FYI – the general user cannot edit the data in the fly-out because they are read-only, but that can read a column which we would prefer they not be able to see.