HI Joe,
By setting the permissions for the Anyone Role, you have given "anyone" or all people in that instance the ability to "order on behalf" of those 3 individual people. Thus, providing the Order on Behalf Tab in MyServices to be seen by all.
For the opposite use case - to only allow those 3 individuals to see the Order on Behalf Tab in MyServices and have permissions to "order on behalf" of anyone the following can be done:
1. Create a Custom Role
2. Add the 3 indi