Syntax is defined as (emphasis mine):
[...] the set of rules, principles, and processes that govern the structure of sentences (sentence structure) in a given language, usually including word order.
Currently there are 34 questions tagged word-order. I would be hard pressed to find a reason to keep the two tags separated, beside the fact that people unfamiliar with linguistics terminology maybe don't know what "syntax" means.
So the tag synonym is warranted meaning-wise, and would yield syntax if someone attempts to type "word-order" in the tag bar.
(I don't have the 5 points required to propose the synonym myself)