Steps to reproduce:
1. Open the project from the attached file "1243391.zip"
2. Go to Edit > Preferences > External Tools
3. In the External Script Editor drop-down select Visual Studio Community 2017
4. From Assets, open NewBehaviourScript.cs

Expected result: Script is opened in Visual Studio 2017
Actual result: Script is opened in windows default Visual Studio version for .cs files

Reproducible with: Visual Studio Editor 2.0.1(2020.1.0b10, 2020.2.0a13)
Not reproducible with: Visual Studio Editor 1.1.1(2019.3.15f1), Visual Studio Editor 2.0.0(2020.1.0b10, 2020.2.0a13)
Could not test with: 2018.4.23f1(Visual Studio Editor not available in Package Manager)

Notes:
- when testing the default VS version is 2019
- to reproduce, make sure that the version set as External Script Editor is not the same as the default version.
- right-clicking on the script and selecting "Open c# Project", opens the correct VS version