You can turn a metric on or off for a particular client. This way, they won't see it in their profile and be confused if they should be tracking it.
To do so, go to your Client's Profile page. Select Metrics or Photos inside the client's profile.
Click Manage Metrics or Manage Photos.
From manage metrics or photos > turn on/off and click the toggle switch.
Any metric that is "off" will not show up in the client's data tab on the web or on the app.
You can always turn a metric back "on" for a client and all their previous data will re-appear.