This is a separate but related topic.
Measuring the frequency at the oscillator out pin tells you the oscillator frequency, not necessarily the instruction clock frequency. On old PICs, that was just 1/4 of the oscillator frequency. However, many newer PICs have more complicated clock chains than that, with a PLL and various optional dividers.
It is a good idea to make sure the instruction clock is actually what you think it is as early as possible. I usually do this by having my main loop initially just toggle a pin. Set up the bank for the appropriate LAT register first, then BSF, BCF, and BRA back to do it again. That should take 4 instruction cycles. You look at that on a scope and verify the pin frequency is really 1/4 of the instruction clock that you expected.