Every company has an invisible line, like the officer/enlisted distinction in militaries, but always undocumented for obvious reasons. Above it are the real humans whom the company cares about; below it are the "resources". ICs are always below the line, except in R&D jobs that aren't available without a top-10 PhD... but most managers are also below the line.
Above the line, you basically write your own performance review because the bosses are your buddies. Below the line, it's miserable, and as you said you're one delay or mistake away from being sent to the Performance Improvement Camps. Almost all first-level managers in a company of significant size (25+ people) are below the line and spend just as much time on humiliating work justification (e.g., status reports) as the guys at the bottom.
You rarely see burnout in anyone, because everyone does their best to hide it. Their performance drops until they quit. Most people just assume that's incompetence, especially with managers.
I see it all the time. The difference is management can often delegate the tasks they're most burnt out on to others.
The overarching issue is:
you need stability/healthy employees at the higher levels, at the lower levels it doesnt matter.
You cant have turn over in management, its a risk to the company. Turnover in engineers, even highly skilled ones, can be recovered from with some extra cost.
And who has to go through all that?
The managers.
Trust me, we don't want it any more than the ICs do. But senior/executive management doesn't feel the pain and therefore doesn't care.
(If we paid you to do some operations task for an hour, that whole amount is a business expense this year. If we paid you to build software that will deliver value for the next three years, we have to take the expense of that hour across the next 36 months, not at all once. It’s a GAAP and a US tax code requirement. In no way do I care if you worked 33.25 or 40.75 hours in any given week other than to have enough data for finance to do accounting and file taxes correctly.)
IC's that I've seen on my end to have a little more latitude to actually design things and have a small amount of independence there, wheras managers are stuck with the 'keep the project going' paperwork, people paperwork, shielding the team from the politics, etc.
(I've personally found a way to sidestep a lot of that, but so many of my previous managers have burned out to the above reasons.)
I think companies really need to work on reducing or eliminating the amount of bullshit ICs have to deal with vs management (time tracking, status updates, on call, etc) or have management do the same amount of bullshit. Your boss may say they understand what you're going through, but they most likely do not have the same level of bullshit being asked of them on a daily basis. They can sit in meetings all day, miss deadlines, and no one knocks them on it like an IC where being a day late gets put on a PIP.