As discussed on our livestream, there are no technical impediments to capturing enrolment data in apps that make use of the Gapple API. Developers could feasibly link contact details captured at enrolment to notifications generated through the Gapple API to support existing manual contact tracing processes. The only change use of the Gapple framework imposes on an app is the order in which an at-risk individual is notified - first by the Gapple OS feature, followed by a call from health authorities.
This analysis assumes Apple and Google won't block apps that include these additional features. It's incumbent on the mobile OS companies to provide assurance to health authorities by clearly elucidating to the public what would constitute abuse of the service.
More broadly, the EU announced a minimum set of requirements for all contact tracing apps across Europe, insisting on user consent, no location tracking, anonymised data and a post-pandemic plan for switching off tracing features. EU academics are meanwhile split over whether to take a decentralised approach to contact tracing (using the DP-3T contact tracing protocol) or to allow health authorities greater control and access to data (the ROBERT protocol).