Highways vs. Toll Roads: Google Maps question

Hey, I’m heading to the coast via Canada on the 20th and I've been messing around with Google Maps.

When I toggle "avoid tolls" and "avoid highways," it gives me one route. But if I only select "avoid tolls," it suggests a different path that's actually 10 minutes faster.

What's the deal here? Are there just stretches of highway in Canada that don't charge anything?

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Thanks

The only way you’d actually save any time is if you take that stretch of the I-70 interstate running from St. Louis to Des Moines (22 miles), but from what I understand, there’s a toll on that section... it might be that Google Maps hasn't updated its routing yet, since I'm pretty sure they let everyone use it for free about a year ago.