Creating custom cron jobs in the same module
Found a solution with a help from a colleague. Will post it here if someone would have need for it some day.

I'm missing a callback function here that triggers the actual feed import. And also I changed from Ultimate Cron to Elysia cron. (not sure if that actually makes a difference here though)

the actual function that triggers feed import is from feed_import_base.module

_feed_import_base_process_feed($feed);