Did you read the comparison review of the Mark I and Mark II?
Pentax K-1 Mark II vs K-1 Review - Introduction | PentaxForums.com Reviews
Differences are marginal, only the AF-S did really increase. And there is the new hand-held pixle shift.
The sensor is the same, so you had the in built in noise reduction with the MK I as well.
There is much to much fuss about this. RAW format was never unprocessed, how should the pixlewise readout of a sensor get into a RAW file without processing the physical data? By a magic wand probably. The sensor manufacturer did a good job by improving the sensor read out and some people think it affects their possibilities, but no one came up with any negative example, on the contrary the K1 is praised for it's outstanding RAW image quality.
Do not bother about that.
Only reason for me to buy the MK I is the pricing.