Shimano SIS rear hub offset question
Yes that's normal for an 80s style bike.  Notice the rear of the dropout slot goes back the same distance, but the drive side has the derailleur hanger there.
You can fit a block in the non-drive side, but having the slot open allows adjustment both ways.  Getting the rear wheel aligned right can be easier if you clamp on the rear brake while doing up the axle nuts, and holding the wheel in the middle of the chainstays while doing the nut up with your third hand.