why does box 12 W say that it's employer contributions even thought it's a contribution through a cafeteria plan

[aschmittlein]

Here’s the info captured in box 12a / code W • W: Company contributions (including employee contributions through a cafeteria plan) to an employee's health savings account (HSA) But, in the form, it says that it is a Employer contribution

[Opus 17]

Because that's how the law defines the plan.  You agree to a voluntary reduction in salary, and the employer makes the contribution.