I've been noticing the same thing more or less. It's also kinda funny how Elliot Rodger was majorly ISFP yet all these "thinking" types sometimes unwittingly emulate his mannerisms as you said-- a clear example of your point about how the wannabes use so much of what you indirectly described as Fi to be Ti or T in general.
Not Fi. Incorrect use of Ti. Even Ti is not perfect.
A heavy basis behind Ti is the idea of
A Priori. If something
is, it is what it is what it is, period. In healthy instances, Ti can be used to seek purity in a theory by weeding out possible points where a theory does or even just potentially
could contradict itself. The risk is that the Ti user will believe things that are
intrinsically logical and have no self-contradictions
within themselves, but also have no
concrete, empirical proof backing them up in their physical environment.
As a statement, it's correct, but if it has no factual substance then it doesn't technically
mean anything -- it's an empty skeleton with no muscles.
Ti relates more to
how objects should behave, while Fi relates more to
how you should move objects, to summarize. Te/Fi is probably the inspiration for "Lawful Evil" -- a Te/Fi user will make his actions consistent with the logical parameters of his environment, but the endgame goal is to manipulate his environs, according to the
environment's sets of logical rules, in order to accomplish
his Fi desires.
This puts Te-users at risk of believing whatever they are told in their environments as according to tangible evidence, while giving no concern for the overall
purpose or principles behind these systems outside of how it benefits them. Fi's intentions may be "selfish" and "wrong," but Te's interaction with its environment are appropriate, regardless of the illogical motivations behind them.*
Think of it this way: Te/Fi is "wrong" but its environment sees it as "right;" Ti/Fe is "right" but its environment sees it as "wrong."
If a Ti-system is based upon what is observed in one's environment, the product it yields will tend to be more consistent. If a Ti-system is based only upon itself, it will yield only the same empty, self-justifying statements over and over and over again:
"A == A because A == A because A == A because A == A"...forever and ever and ever.
*Interestingly enough, it should be noted that a large portion of people who tested to be more Extrinsically motivated in academia than Intrinsically motivated tested as ESTJ on MBTI tests
(though MBTI tests are and always will be subject to countless flaws and can never be trusted to conclusively confirm one's type.)