This is a thin line for both buyer and seller since Both need some kind of assurance of genuine deal .
But it seems little rush to come to conclusion that seller might not be genuine just because he is not ready to share personal details.
Maybe some other ways could have been worked out to between both parties. Since this is a pickup only deal. Buyer and seller could agree to check it out in person and if all is okay transfer the money at that time and take his stuff.
That way both be on safe side.
It does add a little inconvenience for buyer mostly.