I did published the config and changed it by hand but, it seems like a better default to use the scout prefix? So the migrations and the scout doesn't use different values by a wrong config.
I didn't use SCOUT_PREFIX here, cause Elastic Migrations can be used as a standalone package, i.e. without Scout.
I'll give it another thought, maybe it makes sense.
https://github.com/babenkoivan/elastic-migrations/blob/2a1998ad9fd1934bb161e87f675efcc5e7efb6bf/config/elastic.migrations.php#L6
I did published the config and changed it by hand but, it seems like a better default to use the scout prefix? So the migrations and the scout doesn't use different values by a wrong config.