You're right.
The day moves forward an hour......but your body gets an hour less sleep.
Say for instance you go to sleep at 11:00pm and you have to wake up at 7:00 am.
During Daylights saving time at the time you are ORIGINALLY supposed to wake up at 7.....it will be 8 o' clock due to DST.
So you will THEN be forced to wake up at the NEW 7:00......Which would have been an hour ago.
So, In all honesty, Its your body that really loses out on that extra hour of sleep being that you have to wake up an hour earlier according to your Biological Clock