Was just playing around with divergent migrations, i.e. same version but different name.
The Runner has a configuration flag "set_abort_divergent" that does what the name suggests. However, it may come as a surprise that divergent migration are then simply not applied (they also cannot, since the version column in the migration schema has a unique constraint).
There's a lot of error logging going on, it might be worth letting the user know that while the migration proceeds, it is only partially applied 🤷