In the UK I’ve seen this called the “intelligent client” model. Basically a core group of PMs who outsource everything. In my narrow experience of being on the inside of this, it failed drastically as the internal PM team lacked the technical expertise to foresee and plan for challenges, and really understand what was going on. The sea of external consultants all had differing incentives (other than earning money) - and the contracts written weren’t watertight or ever enforced to stop runaway spending.