The project manager should always monitor and control the project schedule and make adjustments as needed to ensure timely completion of the project. If the project manager identifies that some activities can be done faster by other resources, they should review the work allocation and reassign some tasks to shorten the critical path. The critical path is the longest sequence of activities that determines the project duration. By reducing the duration of the critical path activities, the project manager can avoid delays and meet the project deadline.
This is also consistent with the principle of optimizing resources and minimizing waste, which is part of the PMI Talent Triangle. References:
* PMBOK Guide 7th Edition, page 131
* Agile Practice Guide, page 50
* PMI Talent Triangle 1