Except as provided in this subchapter, the definition of "sickness" may not be more restrictive than the following: Sickness means illness or disease of an insured person which first manifested itself after the effective date of insurance and while the insurance is in force. A definition of sickness which anticipates the exclusion of coverage of pre-existing conditions subject to the limitations expressed in Insurance Code §1201.208 may not use the phrase "the cause of which originates" or any similar phrase. The definition may be modified to exclude sickness or disease for which benefits are provided under any workmen's compensation, occupational disease, employer's liability, or similar statute.