Short answer: Yes. An employee returning from FMLA leave must be restored to the same group health coverage on the same terms as before, with no new waiting period or re-qualification.
FMLA is job-protected leave, so when an eligible employee returns, the employer must reinstate their health coverage exactly as it was before the leave; same plan, same terms, without imposing a new waiting period, re-enrollment hurdle, or evidence of insurability. This protection applies to employers with 50 or more employees who are covered by the FMLA.