Why do you say so? TFA goes:

In fact, the "one platform team supporting many product dev teams" pattern is so prevalent that AWS, in true customer-obsession mode, has now reasoned backwards from it to design Proton. Proton is a prescriptive way for platform teams to package up environments and infrastructure services...

Proton is prescriptive in the sense that it gives you a pre-baked pattern for coordinating application delivery, but descriptive in the sense that this pattern wasn’t dreamed up as an arbitrary “best practice” – it’s simply a canonization of what AWS sees customers already doing.