It is surprising. It may be a result of the vendor using its EIN rather than a personal SSN, and the EIN is attached to both the entity name and the person’s name. A sole proprietor does not necessarily need an EIN – their SSN is their tax ID. But if s/he has employees, then s/he needs an EIN; but if s/he’s still a sole proprietor, the EIN will “flow through” to his or her personal name but the entity name (an LLC?) is also affiliated with that EIN.
There is another possibility – if the name on line one and the name on line two share the same letters up through about the fifth position, that would explain it. The TIN match does not actually match to the entire name; it only matches to the first five or six letters in the name. So if the name on line two shares the same first five or six letters, you’re getting a match, but not really – it’s really matching what it considers the legal name (line 1); it coincidentally also appears to be matching the line 2 name, but that’s because it’s not actually matching the full name.
Whatever the reason, the important thing to note is that according to the IRS, the TIN must match the legal name which is to be entered on the first line of the W-9.