You may be correct and rules may have changed during pandemic but usually it takes around 90 days for health card in Ontario. Health cards are not given on Aiports(may have changed now). So in that case you need to buy before hand at least for 2 weeks to cover your quarantine period.
Also, health card does not cover everything. For ex- eyes, dental, physio and many more.
Please check it before travelling.
Moreover, it is always advisable to travel with insurance when you are going abroad. It will cover your travel time also.
Let me if you have better idea.
Thanks
for information
https://www.ontario.ca/page/apply-ohip-and-get-health-card