See if this helps:

Your taxpayer has so many customers, and even though no one pays $600 or more in a calendar year, your taxpayer has a $3 million business. Are you going to wait for 1099-NEC, or are you filing their business taxes?

What about: Your taxpayer mows lawns and does home maintenance, so has no business clients. Only homeowner clients. Your taxpayer makes $30,000 a year. Since homeowners are not required to use 1099-NEC for their services, are you going to file your taxpayer's business taxes anyway?

Both answers = File Taxes using the info you have, because 1099-NEC is informational. It notifies the IRS that a business-to-business event has happened, and one of the things it does is provides the info that the issuer intends to report as business expense. It isn't all about Income.

You already know about the Business; your taxpayer is supposed to provide all the info, not just the parts reported to the IRS.