I agree, its not unusual to hear sound coming from the hydraulic fluid when you’re working it hard.
I hear this sound in my car too and am annoyed by it. I think it might be “cavitation” in the suspension oil. I think it’s air coming out of the oil when the pressure is extremely low: when the oil is experiencing suction from rebound. It’s even possible that the pressure is getting low enough cause vapor bubbles in the suspension oil. Basically boiling at room temperature. I’ve read a few discussions from suspension engineers and even they can seem to decide if it’s from air bubbles being released from the suspension fluid or the fluid itself vaporizing at low pressure.
-Paul from ESG