Enamel, lacquer, urethane? Which paint?

[Grounded63]

Might not necessarily be the case. They may just be more honest.

TCP is just going to mix a formula from their in house brand data base, and send it. ( It may even be PPG, and they may not legally be allowed to disclose it ) If it doesn't match perfectly on your end. That's your existing aged 60+ year old paints problem.

PPG locally, is going to mix a formula of what it would have looked like originally/brand new. According to their data base. Depending on how your original 60+ year old paint has aged. Its probably not going to match perfectly. And will need to be tinted to match.

Also the the paint materials. Lacquer toners/metallics/pearls. That the vehicle was originally sprayed in. Haven't been available for multiple decades. So trying to color match perfectly. A newer paint system to an existing aged 60+ year old paint. Is always going to be a maybe. Especially when a distributor is dealing with a customer/vehicle face to face.

Edit.
Not to imply you are at either end of this spectrum. But, some customers can be especially unreasonably picky. And, others don't even care if the paint actually matches the OEM sprayed finish. As long as it has the correct color name on the can lable. That is also, probably, part of why you got a maybe, also.