Consider the following scenario:

• repo R with packages foo and bar
• release version 1 in the upstream repo
• run bloom-release (all good)
• remove package foo from repo R
• release version 2 in the upstream repo
• run bloom-release...

In this case the second bloom-release call will run the generator for package bar version 2 as expected. But it additionally runs the generator for package foo version 1. While that doesn't do any harm it is unnecessary, slows down the generation, and might confuse the user.