As used in this thread's context,
https://en.wiktionary.org/wiki/veteran#Noun describes this meaning as:
> 1. A person with long experience of a particular activity.
The military version is a bit different:
> 3. A person who has served in the armed forces, especially an old soldier who has seen long service; also called a war veteran to distinguish from veterans who weren't in armed conflict.
The etymology from https://www.etymonline.com/word/veteran is:
> c. 1500, "old experienced soldier," from French vétéran, from Latin veteranus "old, aged, that has been long in use," especially of soldiers; as a plural noun, "old soldiers," from vetus (genitive veteris) "old, aged, advanced in years; of a former time," as a plural noun, vetores, "men of old, forefathers," from PIE wet-es-, from root wet- (2) "year ... General sense of "one who has seen long service in any office or position" is attested from 1590s. The adjective first recorded 1610s.
You can see definition (1) dropped the "soldier" restriction, and (3) dropped the "old" restriction.
I therefore don't think you can apply your understanding of (3) when (1) was meant.
FWIW, there's also a veteran car, which is one built before 1905: https://en.wikipedia.org/wiki/History_of_the_automobile#Vete... .