I think this is kind of a hard question to answer because it is all about a subjective "feel" of the switch. Having used reds and blues that I can compare with browns, I can not say I experience the same stiffness you are describing. There is some light resistance, and while the actuation force is similar for reds and browns, to me browns feel heavier. It feels like you need more force to push the brown switches past its tactile "bump" to register a key stroke.
However, the switches do not really strike me as "stiff". Especially not compared to blues. If you would have had reds before, then I would have understood what you meant. But coming from blues I would not expect you to think they are stiff.