I've seen projects slow walk the early stages when the critical path runs through procurement. Electrical and control equipment usually has very long lead times, so early scope could be detached from the completion date.
It can benefit your risk profile (in case of unexpected stuff underground) to get non critical items started early, it can get very expensive though as you pay site support/management costs for a longer duration.
IMO in large projects there's usually no free lunch, everything is trade offs. Even then Humans simply aren't capable of managing complex projects effectively; effective project management requires the right organization/institution and there's alot of waste no matter what.