These companies are his customers. He's got/is this one business.

1099-NEC is an informational form. If your client drove for 1 or 150 businesses, such as a courier, and if no one paid him $600 or more in the year, he'd never get a 1099-NEC at all. Yet, he would report all of this on the tax form, all revenue and expense. If he drove only for private people and they paid him $1million, he would not get a 1099-NEC, yet he would report all of this on the tax form, all revenue and expense.

The 1099-NEC forms are not the tax reporting paperwork.