Spectre: Being able to block something doesn't change its spyware status.
Q: I play a game built with Unity software, what should I know?
A: Unity has probably collected some or all of the following information about your device: unique device identifiers (e.g., IDFV for iOS devices and Android ID for Android devices) ); IP address; country of install (mapped from IP address); device manufacturer and model platform type (iOS, Android, Mac, Windows, etc.) and the operating system and version running on your system or device; language; CPU information such as model, the number of CPUs present, frequency, and instruction set support flags; the graphics card type and vendor name; graphics card driver name and version (example: "nv4disp.dll 6.10.93.71"); which graphics API is in use (example: "OpenGL 2.1" or "Direct3D 9.0c"); amount of system and video RAM present; current screen resolution; version of the Unity Editor used to create the game; sensor flags (e.g., device support for gyroscope, touch pressure or accelerometer); application or bundle identification ("app ID") of the game installed; unique advertising identifiers provided for iOS and Android devices (e.g., IDFA or Android Ad ID); and a checksum of all the data that gets sent to verify that it did transmit correctly. Some Unity developers use Unity’s analytics and ad services which collect additional information. See FAQs on Unity Analytics and Unity Ads below.
Source:
https://unity3d.com/legal/privacy-policy If you don't like it don't play any unity games. This is part of the platform and your agree to it by buying the license to play the game. The software will fully function if blocked, a properly setup system will always block first.
Alexim: I'm not an expert, but isn't it possible that it just tries to synchronize the achievements with GOG Galaxy?
Judging by the communication and IP's its safe to assume you're right :)