If that were true all the time, then no need to ask any questions at all. When that's not true, the PM needs to know what's remaining....I thought the point of the article was that if you have to ask your leads how long it will take and when they will finish something, then you do not have enough knowledge of the time factors involved in doing the various tasks within your project, or lack a good database of the same, to be a project manager. And that is what I see all the time. Supposed project managers that can't even tell if a sequence of tasks is in the correct order, never mind how long anything will take.
IME PMs tend to be business degrees not technical people, even in the best run offices. That's rather irrelevant tho bc even among engineers there are many who dont understand the nuances of each others' work but need a high-level view - MEs vs EEs vs systems/software folks. If the individual tasks are broken down to the lowest, most simplistic level then even the most ignorant PM should be able to understand them well enough to know "what's left." They might not know how to run a bolted joint analysis for example, but if I have multiple, separate tasks for running BJA on a dipstick fastener, another for intake manifold fasteners, exhaust manifold fasteners, bellhousing bolts, etc then they know the couple fasteners I'm looking at and when I'll be done within a few hours bc the task itself is tiny. Granted, there are tasks which must be rather massive - durability testing where a test stand automatically runs 10k hours or a computer simulation that must run days, but the goal for individual contributors is to get every task broken down to a few hours.
In a poorly run office you gotta do what you gotta do. BTDT, doing that now actually bc in consulting I'm usually at the mercy of customers' PMs & process. If the PM cant/wont compare tasks back to previous projects then your timeline is likely going to change significantly from start to finish. Employees will also struggle to keep up at times and you will waste a lot of time discussing the timeline.
In my (former) best run office we spent very little time discussing timelines. We had three PMs, ~300 engineers, and a small group of marketing/purchasing/other business folks. At the start of each program the team would spend a couple hours together laying out the high-level project plan, then for a few weeks afterward each member would meet with a PM individually for ~30 mins to fill in the lower level. At those meetings the PMs were constantly referring to their database. If I said I needed to run a specific analysis or test they would tell me previous examples took X hours, had Y for a predecessor, and Z for a follow-on task, which really helped take the human factor out of planning. Minor issues/emergency changes aside, everything after that was simply executing. The project plan and tracking was fully automated, you received an email when all predecessors were complete and you could begin work. Once you received the email, you clicked a link to acknowledge starting the tasks and again once finished. If you didnt click start or finish within a few hours of the expected time then your supervisor was notified automatically to address the situation. Other than a cursory couple minutes in monthly design reviews with management, we didnt discuss timelines after the first few weeks of a program nor needed to aside from resolving the occasional issue. Everybody kept a full and very busy but extremely predictable schedule, and our usual 1-2 year projects were usually complete within 1-2 weeks of the original predicted date. The best part tho IMHO was the predictability allowed you to plan vacations and work travel well in advance and not return to a mountain of trouble. I have found in poorly organized offices that there usually isnt a good time to be away, usually when you leave is when you're unexpectedly most needed and there's always a mountain of crap waiting for your return. Coincidentally, in that best-run office I also rarely needed to interact with my manager. We traded emails a couple times weekly, usually for him to approve purchasing or CAD/print releasing, and I saw him in a monthly project/design review with other managers. Management didnt micro-manage, they expected us to do the work, be professional/competent, and communicate occasional issues/questions/concerns as necessary.