Fliegers generally don't have screw-down crowns.
Most have only 3 to 10 meter water resistance.
The manufacturer's page for this watch says 20 ATM or 200 meters, which is hard to
do without a screw-down crown.
So either it has a screw-down, or it has some other method of sealing the crown to 200 meters.
I wouldn't worry about it.