a stock trading platform, as described in the article?

In North America, “engineer” doesn’t necessarily mean a software engineer with a professional certification. Software developers have taken to calling themselves engineers. Whether engineering professional bodies should start going after people for this or not is a different topic.

But it’s entirely possible for someone who calls themselves an engineer to not actually be a certified engineer. So the activity wouldn’t be regulated because the person isn’t part of a professional body that regulates members.

In that case, lack of competence would be a civil issue unless it resulted in something criminal.

There isn't even a way to get certified as a professional engineer for software in the US.

There was but no one did it, so they stopped: https://ncees.org/ncees-discontinuing-pe-software-engineerin...

It is still possible in the UK and I assume EU (chartered engineer and the EU-alternative).

So the reason it isn’t a PE-discipline is uptake, not the work itself.

it's what you're doing (your "function") that's regulated

not your job title, or piece of paper that you have that says you're X, Y or Z

"Professional Engineer" is a protected title that requires licensing to be used for a discipline. That licensing process does not exist for software in the US right now.

Could well be the entity actually selling the services.