Depends on the source. I've been doing nogi BJJ (not on the comp team: I am old, we train hard but not competition hard) about ten years or so.

People training technique will grey out pretty much routinely as they talk through things with their partners and work strategies for techniques.

People go out now and then, usually on purpose with folks who understand when it happens.

The BJJ community is mature at this point. There are folks on comp teams basically having fights every day. I suspect when those people go out, you are right. Damage is done and it accumulates.

I suspect when folks like me and my training partners go out, there is no trauma to speak of.

What is the net of this lifestyle? I don't know; I've had no major injuries (requiring surgery or major downtime-- popping the cartilage in your rib working top control drills will take fucking forever to heal tho), I've learned a lot, made good friends, and have only this life to spend as I see fit, so I can only anecdata.

But the understanding in our world is this: trauma is traumatic (and sometimes causes loss of consciousness, sometimes not), but not all loss of consciousness is traumatic.