The ESTA visa waiver which is the easiest way into the USA for allied nations specifically allows meetings, consultation, training and states that installation of advanced equipment is allowed under that visa.
The question being asked by the parent is if they stepped outside the boundaries of that visa waiver.
When I worked at Salesforce Japan, I went to conferences in the US. I always honestly said it was for business when entering the country. I spent nearly the whole time at the office, and answered emails from customers and clients.
No one asked about visas. I didn't think that was an issue since I really was there for a week for a business conference, but maybe it was? After all, technically it was a "Tourist" visa.
In the end though, SFDC keeps almost all of its technical talent in the US. If the government really got annoying, they probably would have stuck to the local talent and forgotten about the rest of us.
The thing is, that ESTA thing everyone calling American "tourist visa" is not an actual tourist visa. It's a "visa waiver" for "visitors" and basically the US border security recommended option for these business guys.
Technically there are lots of restrictions and actual commercial visas are sometimes required, like you've been to sanctioned countries in the past, or if you're engaging in businesses locally like purchasing materials to export for resale(not even B-1 allows that?), but it's all kind of arbitrary.
There are more options than "tourist" and "working" visa. Your message is significantly oversimplifying it. Until we know what they were actually doing at work (really, not claimed by ice), we won't know how valid their stay was.
