Short answer: Yes, within limits. Employers can vary contributions by legitimate employment-based classes (such as full-time vs. part-time or job category) but not in ways that discriminate in favor of highly compensated employees or owners. Section 125 and Section 105(h) nondiscrimination rules apply.
Contribution amounts don’t have to be identical for everyone, but the variation has to be based on bona fide employment classifications, for example, full-time versus part-time, hourly versus salaried, or geographic region, not on health status. An ICHRA, for instance, permits up to 11 defined employee classes with different allowances.
The guardrail is nondiscrimination: cafeteria plans (Section 125) and self-insured arrangements (Section 105(h)) are tested to ensure they don’t disproportionately favor highly compensated employees, owners, or key employees. A plan that tilts benefits toward the top can lose its tax advantages for those individuals.