> High earners generally do not benefit from unions as they can make more negotiating their own labor value versus participating in collective negotiation which is more likely to drag their compensation down towards the average, even if it's still higher than average.

High earners benefit from unions if union rules are made which benefit high earners.

The most well-known example of a high-earner union is SAG-AFTRA and they provide benefits to established performers, the big one being name exclusivity. e.g. even if your real life birth certificate says your name is "Tom Cruise" you cannot advertise your name as "Tom Cruise". Obviously, actors are still negotiating their own pay.

Another good one is the NFL Players Association which capped the rookie pay scale in 2011 to ensure the salary cap was going more toward veterans, people already in the union. However they still independently negotiate their compensation.

I don't know what people would want out of a tech union specifically but the idea that "union = payscale based on seniority" just plain isn't true.