I qualify this by saying I am not sitting in front of a Mac as I write, so regretfully I am missing a specific. BUT Address Book uses the "card format" (this is the missing specific; I don't remember the exact name), while CSV is a generic comma separated format (most often used with spreadsheets).

Can you export from the server in another format, or is there something that takes CSV and converts it into AB format?

When I get in front of a Mac I will check and see if I can answer my own questions for you, if no one else has beforehand.

On a Mac since 1984.
Currently: 24" M1 iMac, M2 Pro Mac mini with 27" BenQ monitor, M2 Macbook Air, MacOS 14.x; iPhones, iPods (yes, still) and iPads.