You said it yourself - it's a question of engineering versus business roles.
Software engineering doesn't necessarily have a higher bar than other comparable STEM.
And lest we forget many other roles have to pay their dues upfront at a much earlier stage: doctors have the MCAT, lawyers have to pass the bar, many accountants become CPAs, etc.
I've never heard of a civil engineer being asked to design a blueprint in Autodesk with a more senior engineer watching them, or an accountant asked to calculate a department's P&L given 90 minutes and a folder full of Excel files. It might happen, but I suspect it's uncommon.
You're right about exams, but that's a one time thing. New lawyers, doctors, and CPAs have to demonstrate textbook mastery to pass a handful of exams once in their career. Engineers are expected to demonstrate textbook mastery for every job they apply to _for their entire career_ (and often multiple times per application!)
It's also worth noting that engineers have standardized exams and certifications, like CompTIA or AWS Certs, but for whatever reason those credentials do not seem to carry much weight. I've never heard of those replacing technical evaluations, just used to enhance a resume.
Software engineering doesn't necessarily have a higher bar than other comparable STEM.
And lest we forget many other roles have to pay their dues upfront at a much earlier stage: doctors have the MCAT, lawyers have to pass the bar, many accountants become CPAs, etc.