Hah! How about this: So they don't end up injuring themselves.

There's a reason why ergonomic chairs exist and why they all follow the same exact design rules (to varying degrees).

Most important features, in order of importance:

1. Adjustable arm wrests. Height is more important than swinging out/in. The out/in feature is more for convenience of getting them out of the way on occasion than anything to do with ergonomics.
2. Adjustable height. The base of which all ergonomic chairs were developed.
3. Adjustable lean. Meaning: You can control how far back it tilts.

Also important: Men and women have different ergonomic requirements! A woman's spine is curved and should not have the chair configured the same as a man.

My hospital bill for back pain so severe I couldn't even move cost way more than the cost of the chair with proper lumbar support I subsequently bought. That was caused by a cheap executive chair, not gamer chair, though.

The lifetime of the product. I bought an ergonomic chair back in 2016 and it's as good today as it was then. Any gaming chair I've bought never lasts more that 3 years. Spend €600 once or spend €150 every three years. In two more years my chair will be the same cost as having gaming chairs and in three it's cheaper. Much larger upfront cost though.