The restrictions of Viewster are a German issue only, caused by German law. In order to make adult content viewable at any time of the day, Viewster would have to change the parental lock method in order to comply with German law. Currently, Viewster's parental lock is turned off by default. To comply with German law, the parental lock would always have to be turned on, without an option to turn it off. That's also the method used on ordinary TV channels, eg. there are some programs on Syfy which can be watched before 22:00 only if you enter a 4-digit pin code before, and there is no way to turn that off.
https://recht.nrw.de/lmi/owa/br_bes_...n=N&menu=1&sg=