Less freedom to pivot around the rear axle as the brake is stopping it rotating. This then stops the suspension arm moving as much (rather than actually stiffening up the suspension….). Just brake less on bumpy bits
But if I put the rear brake on I can compress the suspension and it moves freely in the car park :-)
I do know why braking is a problem I am asking the question to illustrate that most people just spout what they are told and don’t really understand it :-)
I have moved from a Patriot (single pivot) to a Hustler (4 bar)
I must admit I don’t notice the performance under braking being any better, but that might be because I rode the Patriot for 5 years so got used to not rear braking over rough stuff. What I do notice though is the lack of pedal feedback on the Hustler when climbing. Going over a root or something, I could feel pedal force increase/decrease.
Patriot in general felt much more active though, Hustler seems to steer better though