I think that I'm being misread here a bit.
Or perhaps misinformed.
I was simply curious if the 1m BTC that I'd heard about
It is a rumor. Some people did some guessing. Then they did some maths with their guesses.
If their guesses are correct, then they have computed that perhaps Satoshi has approximately 1 million bitcoins (give or take a few hundred thousand).
If their guesses are incorrect, then their computations are meaningless.
was instamined or if it was mined prior to announcement?
No. Bitcoin did not have any mining prior to announcement. Bitcoin did not have any instamine.
Obviously there wasn't a short term incentive to liquidate if all or even a majority of the coins still exist.
Nearly all bitcoins still exist. Relatively few have been destroyed. I think the total amount of destroyed bitcoins is less than 150 BTC.
Charlie Lee's exodus from LTC was surprising to me, and it showed that not everyone is committed to the same ideals as Satoshi.
Satoshi is probably dead.