Consider the following scenario:
You install Microsoft Exchange Server 2019 Cumulative Update 12.
You enable extended protection by running the script.
You try to log in to an Exchange Server 2019 mailbox in a coexistence topology.
In this scenario, Outlook on the Web (OWA) doesn't allow you to log in even after you enter the appropriate credentials.
To fix this issue, install Cumulative Update 13 or a later cumulative update for Exchange Server 2019.