Yes. I can confirm that mileage can be adjusted.

I previously went to view a used 2012 ER6 from a private dealer. After arrived at his place on the agreed time, the bike still haven't arrived yet.
I found out that it's a Terengganu bike, he bought it from a private seller there and tow the bike all the way to KL.

He called the towing-guy. The dude said will arrive in 10 minutes, got some delay because of the jam.

So I just waited there, and I am the first person to view the bike. Checked everything, the mileage of this bike was around 60K km.

The next day, I checked on Mudah. I saw that exact bike.
Same black color, same number plate.

The mileage on the picture was shown at 16km. Jeez.
Then I knew that the mileage is not original.

Never went back to the private dealer anymore.