A valid visa possibly but not one valid for the type of work they are doing, which would have required an H1B. The article doesn’t seem to address this head on.
Its right there in the link the parent gave. As in they had a visa and ice acknowledged no violation of the terms of that visa in very plain english.
I have stamps from the US border that literally say B1/B2 on them.
If anything is undermining anyone's credibility here, it is not the article doing that.
https://en.m.wikipedia.org/wiki/B_visa
There's also a picture of such a visa.