I don't find the claims made by an immigration lawyer representing the workers to be particularly persuasive, just like I don't find the claims made by the local union rep about what they "believe" the workers were doing to be persuasive.

People and companies can and do write whatever they want in letters submitted with visa applications. That has no bearing 1) on what you are actually allowed to do given a certain visa type, and 2) what the worker actually ends up doing.

In other words, the visa applications may very well have been valid and approved on that basis, but the applicants might have been engaging in other activities that were not permissible. This is quite common - people will say "I want to go to Disneyworld" when they actually intend to overstay their visa, or "I want to visit family" when they actually intend to work as a nanny or cook for a few months, then return home.

I'm not saying this raid was conducted properly or that all the arrests were justified, but I do think the reporting on it has been almost negligent. In contrast, here is an old article written by an immigration lawyer discussing the complexities of the B-1 business visa: https://blog.cyrusmehta.com/2016/05/the-b-1-visa-trap-for-th...