The reason why paying bi-weekly helps you save more interest and pay the mortgage faster is because there are months where you send more than 2 payments.
So for example, if your bi-weekly schedule started on Nov 1, 2020 then your payment will go through on Nov 2 (because Nov 1 is on a Sunday). The next payment will be on Nov 16 (2 weeks after and because 15th is on a Sunday). Normally, you only pay 2 times but on this case, you will be paying a third time on Nov 30.
So if you compare it with bi-monthly payments, you send more payments if you do bi-weekly payments. Bi-monthly payments, you only send 24 payments (no more, no less) a year. As for bi-weekly, you send more than 24 payments in a year (depending on the date you started paying). And the more payments you send, the more payment goes to paying off the principal.