As for the C172, the speeds quoted in my own POH are INDICATED airspeeds and nothing else.
Quite right too. If it was not that way then how would use the instrument that provides INDICATED airspeed as a reference.
Of course TAS is taken into account when measuring performance but that is done by applying pressure altitude and temperature to the appropriate tables.
The test pilot will have checked PEC and there will be a table or graph in the book.
However, the test pilot will also have tested the appropriate approach speed and used that to determine the performance and certification.