"... The first ADC conversion result after switching reference voltage source may be inaccurate, and the user is advised to discard this result."
Waiting 100 uS, and taking a reading and discarding it, are two totally different things.
"... The first ADC conversion result after switching reference voltage source may be inaccurate, and the user is advised to discard this result."
Waiting 100 uS, and taking a reading and discarding it, are two totally different things.