24D - Absence Type Configuration for BPM Task Expiration

Currently we are using only one approval rule for absence like 1=1 and approval required by line manager and expiration is set as do nothing.

When it comes to this new feature, for existing absence types it is blank and for new absence types it is reject by default and there is no blank option. here I would want to know the impacts and all. also is there any way to keep this option "Action on BPM transaction expiry" as blank for new absence types.