Apparently in Canada, mortgage interest may compound semi-annually, which might explain the difference.
Using the math on that page, I derived a monthly interest rate of 0.0041239 on your example loan. When multiplied by the principal of $100,000 I got a first-month interest fee of $412.39
This page walks through the math to derive a Canadian mortgage cost:
https://www.mikesukmanowsky.com/blog/a-guide-to-canadian-mortgage-calculations
Apparently in Canada, mortgage interest may compound semi-annually, which might explain the difference.
Using the math on that page, I derived a monthly interest rate of 0.0041239 on your example loan. When multiplied by the principal of $100,000 I got a first-month interest fee of $412.39