Cohorts are based off of your employer, because we, inexplicably, tied health insurance to your employer. If you work for a very young and hip company then no, your cohort might not file claims.
There's levels of broken-ness to healthcare in the US. Even if you allow health insurance to discriminate based on health conditions, it will still be broken in other ways.
That's one way, true. I've mostly been considering the ACA here and those getting coverage that can't get it through an employer.
Employer health insurance rates fan still get wonky for small businesses though. It probably can't happen today, but I was at a small business where everyone's rates went up shortly after one person was diagnosed with cancer and another one or two with diabetes.
That is an example of it not really being individual insurance though. The insurance company is just lumping the employees together and setting rates based on the relative risk of the whole group, not dissimilar from getting an individual policy where the rates are based on a group of one.
There's levels of broken-ness to healthcare in the US. Even if you allow health insurance to discriminate based on health conditions, it will still be broken in other ways.