Coplanarity use Profile.
Flatness is an individual control.
When you want multiple surfaces to lie in the same plane the
Y14.5 Standard says to use profile. Many designers and
engineers think that if flatness is used in conjunction with
an extension line, it means that the surfaces must be
contained within two parallel planes with a maximum separation
not greater than the specified flatness tolerance. As
illustrated, however, this is not the correct
condition is called coplanarity. The correct method to
control coplanarity of multiple features, is by using
profile as illustrated below.