It’s part of an effort to have dedicated managers and dedicated engineers instead of hybrid roles.
This is being sold as an efficiency win for the sake of the stock price but it’s really just moved a few people around with the TLMs now 100% focused on programming.
As far as I can tell, the main function of an EM is to enforce the company policy. I'm not sure there really is a need at a smaller place.
In a small company (let's say anything under Dunbar's Number), you have a very dense network organically, and EM's aren't necessary. As the company grows larger, the matrix becomes sparser and sparser- until you get to something like Google (180k employees plus maybe that many again contractors) and you have almost all 0's. So an EM's job is to solve the communication problem, because information still needs to flow around the company, in and out, whether it's "do this project" or "another team already solved this problem" or "this project is a never-ending world of pain and should be ended" to "employee 24601 is awesome and should be given more responsibility."
Probably the best description I've heard of the EM role is that "It's a large collection of part-time roles, all with disparate skillsets, that together are responsible for ensuring the success of the project."
Communication is a huge part of that - downwards (telling reports the information they need to be successful), sideway (getting information from cross-functional partners and managerial peers so you align your projects with theirs), and upwards (managing expectations and asking for direction at the appropriate point so upper management doesn't freak out).
But other skillsets involved are: playing therapist (managing anxiety, morale issues, resentment, and misconduct); coaching (both technical and interpersonal); splitting up vague exec mandates into subgoals; prioritizing; hiring; managing performance; serving as a point of contact for whatever random problems your reports bring you; negotiating; setting team structure; developing expertise among your reports; managing their careers so they get promoted; ensuring that they're recognized for their accomplishments; helping people have fun in the office; modeling a culture of respect; selling new product initiatives; and yes, enforcing company policy.