To be clear, the wiki definition, or the Oxford Dictionary, or Chambers, or whatever, is only the definition that whoever wrote the definition decided on. It’s useful as clarification or as a pointer if you really don’t know how to use the word. That said, even if it is wholly and exclusively correct* then the understanding of commitment remains open and as it happens, I think that people procrastinate quite often over tasks to which they are committed. I don’t think that commitment implies the complete and unswerving focus on completion of or adherence to a task, or even necessarily the knowledge that one is committed to it.
*which it isn’t