When the mental burden of integrating existing libraries, through tons of wrapping/boilerplating, such as it is with JNI, starts to overshadow rebuilding the same thing, at your current application layer, it's close to a zero value proposition.
That's a lot of negative assumptions you're making. And, IMHO, still not enough to warrant or in line with saying "that's almost the same as not having support at all."
It is very similar to having no support at all, since any language supports calling any other language by way of manually written bridges and wrappers – so if that's "support" then the set of languages without such support is empty.