Logically they can only be giving an educated guess with smaller companies. For example - my SaaS company's revenue estimate in one of these platforms (not Zoom Info, but simialar) was about 25 times what it actually was. Do you know as fact any company's revenue and you can compare that to what Zoom Info has?

Accuracy of revenue size was about 50% for us looking at companies in the lower middle-market. Accuracy of contact person and their contact info was probably 70% if I remember correctly. If I calculated the leads that had accurate revenue, accurate contact info, owner wasn't already exited, accurate industry, and the company info wasn't a mix of two companies w/ similar names: the number drops to about 50%. That means I still have to validate all the info prior to or at initial outreach. It sucked when a team member spoke to a roofer thinking they had $40M in revenue only to find they were a solopreneur with $150k in annual revenue.