upgrading - posting batches in AR and AP reqd?

Upgrading a customer for v2012 to 2017.

The upgrade notes say that posting batches in AR and AP is "optional" in the section heading, then says it is required in the detail.

The customer has a lot of unposted batches in both modules.  I know they "should" post these and I did ask them to do so, but they didn't.  And no one home to ask today.

Do I need to stop and wait for them to post the batches or is it ok to move forward?

TIA