I think the problem is a matter of interpreting Jung's text there (which just seems so hard to digest as it is, for some reason), so different people (including Myers, etc) emphasized different aspects of it.
What I have found that seems to fit best (especially in comparison to the other functions), is from Lenore Thomson's definitions.
Fi is about a "personal connection" to an evolving pattern. Personal (F) as opposed to impersonal or technical, basically (T), and an evolving pattern basically being a "variable" (as termed for Ti) that an individual picks up and internalizes, rather than an agreed upon (external) set of personal standards (or what I now term "established").
That seems to be the most concise way to decipher Jung's above quotes.