WebEngine not starting on properly when deployed with specific structure on Windows

Application using WebEngine used to work with structure similar to this in 5.15, but does not anymore in 6.8.0. (Back then deployment put the webengineprocess.exe next to app.exe.)

Deploy an app, for eg. simplebrowser, with windeployqt and setting libdir one level up of the app executable.

app\
├─ simplebrowser\
│  ├─ simplebrowser.exe
│  ├─ plugins\
│  ├─ resources\
│  ├─ translations\
├─ lib\
│  ├─ qt.dll
│  ├─ qt.dll
│  ├─ webengineprocess.exe

Make libs findable and set QTWEBENGINE env variables. (With this new structure webengineprocess.exe needs steps to be found.)

Error popup seen

Log prints:
[26584] [26584:20460:1126/155600.249:ERROR:sandbox_win.cc(1034)] Failed to launch process. Error: 18

after pressing no
[26584] [26584:32216:1126/155602.106:INFO:web_contents_delegate_qt.cpp(282)] ProcessGone: 7 (18)