/setworldspawn from the console changes the world spawn and hence spawn chunks.
Spawn chunks are loaded and ticking but are not given 'random' ticks. This means (for example) that items in spawn chunks will be moved by water. Will despawn after 5 minutes. Etc. But crops and trees will not grow, leaf blocks will not despawn.
This makes spawn chunks a dangerous substitute for a chunk loader if you are intensing to power your base off of biofuel or charcoal as all your machines in spawn chunks will continue to consume power but without crop and tree growth the power system is starved of inputs.
Systems that force grow crops/trees using magic or power might be able to get growth despite the lack of vanilla random ticks. No promises.