I haven't seen any correlation between instinct stackings and socionics types or enneagram types. They are fully unrelated imo.

The stereotypes, however, would match sx-instinct to being Fi-valuing, in the way that both are described as being about relationships. This has been a moderate source for mistyping Fe-valuing sx-first people into Fi/Te types. Just like social-firsts get mistyped as valuing Fe.