Because RunOnce always starts the target program elevated, Burn needs to cache the bundle into the package cache (or other protected area) to be secure. In order to allow the user to clean up their machine, Burn is registering in ARP to give them a way to clean the cache. The ARP entry is confusing since it implies that the installation is complete. To avoid this confusion, Burn needs to make sure the ARP entry does not exist by the end of step 8.
Relax the requirement that there must be an entry in ARP while any part of the bundle is cached. This allows Burn to remove the ARP entry by the end of step 8 while meeting all of the other requirements.
It is unacceptable for any possibility of the bundle being cached without a corresponding ARP entry. The ARP entry must always be written at the beginning of the chain.