You get at the issue I've seen with what you say here: >I get that there will always be some power dynamic between manager/managee, but I felt encouraged enough with my previous manager's and skips to be open and direct about problems if there were some.

Namely, I've seen too many situations (both as an engineer and a lead) where the engineers really did NOT feel encouraged to be open; and even if it was encouraged, there was not necessarily sufficient trust to be entirely candid. As I gestured at earlier, sometimes the problem _is_ management, and even when it's not, it can sometimes be a risky proposition to be too negative to your boss (ESPECIALLY if they're a component of what needs to be addressed), so I've seen engineers default to limited disclosure.

So what I mean when I say "spy in the ranks" is something more benevolent than I think I conveyed. Namely, someone who is able to bridge that communication gap by conveying the "risky info" in a way that doesn't put anyone in the line of fire; consider the benevolent motive of "This affects all of us and I might as well put my neck on the line to try and get it fixed if other engineers are nervous to put theirs." I mentioned that I was largely poking fun at my past self, so I'll give a concrete example:

I've been on a team after a manager change. There was discontent on the team, because the prior manager had committed to but not managed to complete some QOL things the engineers has requested prior. The new manager was not really aware of this, but the engineers, having been burnt, were not super eager to spend time/effort/political capital to re-surface the issues, even though if addressed they would make life substantively better. I was in the lucky combination of both having some prior rapport with the new manager, as well as having a more senior role that gave me more confidence to "make waves", so I was able to slip in a comment of, "you know, there's X issue that you might not have been aware of. Not going to name any names, but it might be nice to re-surface this."

So to your point: is a culture of open sharing the goal? 100%. And I would be remiss to use the word "Eavesdropping." I wouldn't recommend an avenue to this information that requires "listening in" such that it would break trust. I primarily intend to convey there may be ways to get that information as a process of _building_ trust; the trick here (and why I use the difficult words) is to find the most effective ways to get to the real and honest ROOT of that, which can be hard to bootstrap from a trustless environment, and often requires finding some way to connect with engineers who can see the whole picture and will give you the straight and narrow, ideally in a blameless fashion. (Further to your point; that aspect (blameless) is something very important to build in this conversation, making it VERY CLEAR this is a culture of mitigation and improvement, not fault. Makes it easier to have more of these channels open and conversations in the future)