Possible a regression from the addition of extension.json - https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/LogoFunctions/+/509154/

There is no merge strategy on the config, which means the array is reordered (by use of merge_array) and the numeric key (the namespace in this case) is not prohibited.

try "merge_strategy": "array_plus" and use a default of {} to indicate a key-value array

https://www.php.net/manual/en/function.array-merge.php

Thanks. >.<