On 2012 c63s has anyone noticed that the downshifts from 5 to4 to be bit more pronounced? My car only has 350 miles and I'm interested to know if the MCT will adapt to driving styles?

Don't know the ratios of 4th and 5th but you might going from an overdriven gear to a 1to1 gear.

I haven't noticed but will pay more attention to see if mine are as well.

I did when the car was new. Took about 1000km for the transmission to adapt and go away.