Not sure what you mean by that. When Row Owners are set, they apply to all columns. The reason was asking is because if you are using Row Owners, then there is no easy way to check if a Phone Number is already in use. You would basically need to maintain a separate list of the numbers of all users somewhere that isn’t subject to Row Owners. And then of course you have the problem of matching numbers. Any given number can be written in many different ways. Take for example the US number: 212-456-7890. That could be written as:
212-456-7890
2124567890
212-4567890
+1 212-456-7890
+1 2124567890
etc…
All valid variations of the same number. So it gets a bit tricky.