Managers do this? right, right. I would say managers at best dont mess it up. Creation and maintenance of high performance team comes from within. The surrounding support certainly helps, but to say a manager creates and maintains this is a bit of a stretch.
"ensuring other needs of the business inform that high performance team"
I have found if it needs to be known or communicated it will happen. High performance teams are not just coders (another fail from managers) they are intelligent people who can read and write emails and know how to speak to other humans. This may be the stereotype of some hot pocket eating teenager in a closet from the movies but that is certainly not the case in most professional environments.
For the second, of course they are. You have to take the two statements I made together. There is a spectrum; at one end are devs working on what they feel is important, but not knowing they're not working on what the business feels is important. At the other is the business deciding everything the devs do, oftentimes changing priorities every week. Having one person as a middleman there can be immensely helpful. That may look like a manager saying "Hey Bob. Jane has this need; work with her to understand and implement it", and handling everything off to a dev, but the point is that the manager, A. Gave Jane (and everyone else) one person to reach out to initially when it came to their needs of the team, B. Helped determine that Jane's need was a priority against all the other needs, and C. Gave Bob permission to ignore all other incoming requests and direct them back to the manager, to focus on Jane's need. That is not to say Bob is not reading and writing; it IS to say that Bob can benefit from someone keeping him from being interrupted by every person in the business with a need who thinks he might help.
The point is two-fold. First, creation and maintenance of a high performance team as the company grows is worth someone focusing on, not just hoping it happens organically (sometimes people, especially new hires, need to know "yes. You are really free to make this decision yourself. I'll back you on it." Likewise, sometimes people doing good work need someone who can spend the time to highlight the value of it to the rest of the business, to effect a promotion). Second, ensuring other needs of the business inform that high performance team, WITHOUT interrupting it, are also worth focusing on.
These are both true regardless of the environment, but become bigger needs the larger the company is.