An email finder that returns a plausible-looking address it has not checked is handing you a bounce. Bounces cost connects, and more importantly they cost sender reputation, which is the expensive part.
Find Email now validates the address it finds before writing it to the lead. Addresses that fail validation are not written, so a lead either has a deliverable address or is visibly missing one — and you can filter on that rather than discovering it during a send.
Verification uses your own vendor account, so you control the rate you pay.