Maybe I read over it, or it’s hidden incorrectly in the ‘low self-esteem’ or ‘task aversion’ category, but what I see with myself and my peers is that the biggest reason for procrastination is the perceived ability to do the task. “I need to write an essay, but I don’t know where to start” or any other task where the steps from now to finished thing is fuzzy, unclear, tricky, scary, or all of the above. I see so many people struggling with procrastination actually struggling with generating the activation energy necessary to start and subsequently not losing steam. None of that seems present in this meta-analysis in a way that I find matching my experiences.
Would that not sit under task aversiveness? That is, due to the fuzziness / scariness / complexity of the task, one to seeks to avoid it until it can be put off no longer? I can relate to your description completely, btw. (In fact, it's the reason I found myself looking up procrastination.)