Using Exchange 2013 cmdlets with Exchange 2019 Schema

We have Exchange 2013 with Skype for Business 2015 within our infrastructure. We are working to remove SfB 2015 but will not have this completed within the 90 days of throttling allowance for old Exchange Systems https://techcommunity.microsoft.com/t5/exchange-team-blog/throttling-and-blocking-email-from-persistently-vulnerable/ba-p/3815328.

We want to install an Exchange 2019 server as the bridge for sending to Exchange Online as we have been told this will suffice in stopping the throttling issue for now. 

Since Exchange 2019 does not support UM, if we update the Exchange Schema to 2019, can we still use the Exchange 2013 cmdlets that are associated with Unified Messaging until we remove the SfB 2015 existence? All the mailboxes associated with SfB will still be on Exchange 2013 servers.