Ah yes, that's an institutional difference in how engineering sign-off works. In the U.S., you do usually need engineers with P.E. certifications to sign off on a project, and in small firms it works like you describe. But in large corporations, there are typically
very few people who do official sign-offs, often only the VP of Engineering or head of a project, who signs the final designs, and anything legally deposited with a government. And they usually don't do it purely on their own professional judgment, but only after consultation with the legal department.
As a result, very few engineers actually have jobs with sign-off authority/responsibility. Even if you do have a P.E. certification, unless you're very senior you'll probably never be officially signing off on anything as a regular employee. Below the top levels, almost all engineering jobs are structured as someone doing internal technical work for the corporation that gets passed upwards for eventual sign-off. That's part of what makes the engineering/technician boundary fuzzy, because nearly everyone is a technician by the classification you describe, in the sense of someone who doesn't independently sign off on engineering work (I do agree that engineering involving more design work is a common differentiator, though).