When I wrote the answer (that is currently top answer) I was thinking about a longer time window for the "new manager" period, perhaps a year instead of a few w

When I wrote the answer (that is currently top answer) I was thinking about a longer time window for the "new manager" period, perhaps a year instead of a few weeks. You're right that someone new to the team and new to management won't be able to accurately assess who the top and bottom performers are in their first few weeks. Same for how to allocate resources. If the "new manager" period is the first year of management then I stick by my answer on those points.