Correct. This waiting period applies also to returning residents.
From the official OHIP Web site:
Eligibility
Ontario residents are eligible for provincially funded health coverage (OHIP). To be eligible for Ontario health coverage you must :
- be a Canadian citizen or have immigration status as set out in Ontario's Health Insurance Act, and
- make your permanent and principal home in Ontario, and
- be physically present in Ontario 153 days in any 12-month period.
OHIP coverage normally becomes effective three months after the date you establish residency in Ontario. The ministry strongly encourages new and returning residents to purchase private health insurance in case you become ill during the OHIP waiting period.