Because EXO V1 will eventually be deprecated due to the security concerns around Basic authentication. So Microsoft suggest user to use due EXO V2 module,
And The Exchange Online PowerShell V2 module (abbreviated as the EXO V2 module) enables admins to connect to their Exchange Online environment in Microsoft 365 to retrieve data, create new objects, update existing objects, remove objects as well as configure Exchange Online and its features.
You could check which commands are only available online in the following document.
Or which commands are only available in Exchange online.
https://docs.microsoft.com/en-us/powershell/module/exchange/?view=exchange-ps