For a team that size, you would assume the manager is only spending around half of their time on people management and probably around half their time working directly on whatever the team does. It can be a good arrangement if the goal is just to give a little more leverage to the manager, but it's also equally possible that the manager doesn't have time to do anything particularly well. Also, a lot of time a part-time line manager like that won't have enough organizational clout to look out properly for the team.

Having tried that arrangement a few times, I think it's better to have small pods where everyone is an engineer and then all the pods report up to a dedicated people manager.