I was thinking on a more basic level than UG; just the presence of linguistic universals [1]. I agree that functional languages are in a certain way more expressive than imperative ones, but that seems mostly orthogonal to the syntax of the language.

I’m thinking about basic stuff like improper nouns, denoting a clause’s role by inflection or adposition instead of word order, and having a clearly defined spoken representation- none of this is specific to which abstract structures the language is describing.

https://en.wikipedia.org/wiki/Linguistic_universal