> after two/three years all the juniors in the "surgery team" model start looking at position of seniority within or outside the company, causing high concentrated turnover in such built teams

Is that a problem?

I mean, the same thing happens with literal surgeons/doctors and residency, where their early years of career eventually end and they expect a mid-level position in the organization.

It sounds like a healthy industry that juniors/apprentices work under journeymen and masters at a large organization early in their career, then move up or branch out after a few years.

I'm not sure why companies expect to be able to cost-optimize away a functioning economy, but remain in business.