I noticed in my development environment that the oik custom CSS file was specified as oik-custom.css but was not present and produced a 404 in the Chrome console.

In live ( blocks.wp-a2z.org) this problem didn't occur.

It turns out this was part of oik's logic to decide whether or not to enqueue the file based on the timestamp of the file.
It's affected by te value of WP_DEBUG.

When false, as it was in development, then an attempt is made to load the file if specified.
When true, as it is in live, the it's only loaded if present.

I think the answer is "No, don't deliver oik-custom.css, or custom.css for that matter. It's not needed".