A small update. I have just tested this c++ code (VTK_MODULE_INIT(vtkRendererOpenGL2); was only added on top) with vtk 8.2 and it gave me the output that seems correct:
C++ output
seconds 0.000812054
seconds 0.000779867
seconds 0.000838995
seconds 0.000784159
seconds 0.000291109
seconds 0.000329971
seconds 0.000452042
seconds 0.000813961
seconds 0.000782967
seconds 0.000813007
seconds 0.0007689
Total FPS: 130.022
AVERAGE FRAME RATE: 59.9952 fps
Trying the same fix for version compiled with vtk 9.0.1 made no effect.
Also, a version 9.0.1 was compiled and tested as offscreen, 8.2 with x11 (linux system).