Why are my app reviews deleted so often and quickly since iOS 10.3? Has Apple made it easier for devs to shoot down unwanted app reviews since 10.3? (Maybe 10.3.1, but surely around that time I noticed it.)

I tend to write app reviews that are critical in nature but still constructive and I use a respectful language. I rarely write glooming 5 star reviews however.

What I notice is that eg I write several reviews in the evening and the next morning they are gone. They are not only not showing up in the AppStore but in the list of all of my reviews I can check on my iPhone it appears like I have never written them.

I use a German AppStore account, review mostly apps made by German devs, and because the deletion of my reviews is sometimes happening so quickly I assume that the devs can delete reviews themselves, right? Can't imagine that Apple hires people in CEST to shoot down reviews within a few hours of writing them.

Can anyone please explain what's happening? I could understand how devs view their apps as part of their brand and don't want to get it tarnished by non favourable reviews. So if it's that and Apple is cool with that and supports these kind of devs, more power to them.

I'd just like to know about it so I can eventually think twice about writing an app review when chances are big that it gets deleted as well.
Developers can not directly remove reviews but Apple's App Store staff can.

Developers can ask for inflammatory, misleading, or concerning reviews to be removed from the App Store and Mac App Store.

When a new version of an application is released on an Apple App Store, existing reviews can be archived and removed from immediate sight. This may be the behaviour you are seeing.

Regarding time zones, Apple appear to have review teams covering all time zones. Reviews of newly submitted applications occur on weekends and most holidays. Thus it is reasonable to assume other app store services are available at all times.