The deprecated but still supported style.local.ini isn't used as cache dependency for the CSS output anymore as it was removed from the cache dependencies here:
https://github.com/splitbrain/dokuwiki/pull/262/files#diff-b27513f477b02a62c93f7f9dd40511ddL77
I think this line should be added back to the CSS cache dependencies as long as style.local.ini is still supported.