While it doesn’t have any automatic braking that I noticed, the rollers in the short dirt section presented opportunity to hurt people. (was it dirt? I thought it was) Short laps meant were great psychologically for me as progress was clear and I could mentally tick them off and count down to the end of the race more easily than I can just based on distance.
An 8 lap race was a mere 22 minutes for me - short enough to go hard (for me) and not worry about having to suffer for too long. Although I was recently downgraded to cat C, I finished in the top half of the B race I entered. (in Zwift itself, anyway - just in the bottom half on ZP)
More of these please, Zwift.