Japt, 6 bytes

Outputs false for true and true for false.

ü mÊdÍ

Try it or run all test cases

ü mÊdÍ     :Implicit input of integer array
ü          :Group by value
  m        :Map
   Ê       :  Length
    d      :Any truthy (not 0)?
     Í     :  When subtracted from 2