I've a RT 11mtr pole and a shimano pole. Both flex a little (The shimano is more rigid) but are still much more rigid than my previous poles. I use superlight brushes & a DIY Bentley style brush and can raise the pole from horizontal fully extended (40' with sections from both poles used!) no problems,.. but I would imagine a heavy brush would cause problems.
Fishing poles are quite fragile,.. but then even the proper poles like the SL2 aren't indestructible!