The amortization schedule doesn't change, at least for US mortgages.
The first bi-weekly payment is just kept in a special servicing account. When the 2nd bi-weekly payment is paid, there's enough for that month's mortgage payment. Eventually, over a year, your bi-weekly payments will overlap a month -- kinda like when someone gets paid 3 times in a month if they were paid bi-weekly.
Let's start this plan on Feb 1, 2019.
Feb 1 2019 - 1st payment
Feb 15th - 2nd payment, making a regular mortgage payment on 3/1
Mar 1 - 3rd payment
Mar 15 - 4th payment
Mar 29 -- 5th payment, due on 4/1 but there's an extra 2 weeks there. Boom! Principal drops more than expected.
Apr 12
Apr 26 -- 7th payment, enough for the 5/1 regular sized mortgage payment
etc.
Eta: Apparently, some banks/servicers just hold the excess until the end of the year and then make an extra payment to principal. It'll be in the fine print.