its not synced currently its just an import so it should currently take names from adress-book only on first import of it / that contact.
see Funktionsunterschiede - #7 by r10s (it’s german so some of you might need to use an translator, I’m sorry for that, but anyways this messsage more or less already says whats written in the linked post)
Sure adding another tier / db column for it could be an solution, but the one that implements it should not forget to also add synchronization, so that changes from the address-book are picked up by DC.