Each specific Box on each form is meant for a specific purpose and has its own reporting threshold. So, although they did not need to file like you describe, it's not wrong that they filed.

1099-Int Boxes 1, 3 or 8 have a reporting minimum of $10, for instance. Not everything is "report it when it hits $600."

The 1099-Misc Box 1 would be used when someone is compensated for a lease payment for some specialty tool, for example. In construction, someone might have brought a Grader to the site, and wanted to charge for operating time and use of the equipment, but wasn't also the operator. Or, specialty welding or concrete equipment is listed like this.

1099-NEC is what used to be Box 7 of the 1099-Misc and is for labor.

It also is not used if the payments are made through a third-party settlement entity, such as credit card, Venmo or PayPay or other bank app.

And of course, these are not reconciled to the tax reporting. They are informational. Your client has proof of expenses they intend to write off as business costs, but that isn't their only cost, just as that might not be the subcontractors' only income.