The problem with that logic, as correct as it is, it's still wrong.
The referees look at this stuff.
Discuss decisions.
Reassess what's been awarded.
Alter their perspective of what constitutes a foul, within the framework set down.
For all we know, the ref's analysed Lamptey's penalty came to the consensus it was a shocker and concluded the 'players should be allowed to play'.
Directly resulting in today's joke decision, which for all we know could result in a tightening of the 'forearm smash to the ground' law.