How to reproduce:
1. Open cmd and write the following:
cd C:\Projects\Unity\HubBug_01
set PATH=%PATH%;C:\Projects\Unity\HubBug_01
set FOO_BAR=HelloFooBar
"C:\Program Files\Unity Hub\Unity Hub.exe"
2. In Hub, open "HubBug_01" project
3. Observe Console

Expected result: "Path: C:\Projects\HubBug_01" and "Foo bar: HelloFooBar" are printed
Actual result: "FOO_BAR not defined." is printed, nothing about path is printed

To get the expected result rewrite step 1 with last line changed:
"C:\Program Files\Unity\Hub\Editor\2019.1.1f1\Editor\Unity.exe" -projectPath

Reproducible with: 2.0.0
Not reproducible with: older Hub versions (user states, I was unable to test)