According to me. As a TA for 20+ years I've never recommended flying in the day of embarkation because of the inherent risks of literally missing the boat. The possibility of being unable to board at the next port exists as was pointed out in post 14. I'd recommend OP try and find another way to arrive before embarkation day even if that means an alternate routing and change fees.

It's unfortunate your TA didn't highlight the risks of flying in on day of embarkation and offer alternatives so you could've made a more informed decision rather than be in the spot you're in but I would really recommend avoiding the 70 min. connection at YYZ as beyond airline delays there are a host of other issues which may pop-up including but not limited to red alerts for lightning, delays at security/customs, or even airline problems with its IT as happened in recent days.