(a) a deceptive, misleading, or false notion, belief, etc.: That the world is flat was at one time a popular fallacy.
(b) a misleading or unsound argument.
(c) deceptive, misleading, or false nature; erroneousness.
(d) Logic. any of various types of erroneous reasoning that render arguments logically unsound.
[1] to paraphrase "The Princess Bride"
No, it doesn't.
Government: - "We will use data just for medical purposes"
Government (later): - "Guess what, we lied/we recant: we will use them for other state purposes too".
There's nothing fallacious in (a), (b) or (c) way about either statement or the whole situation.
(a) a deceptive, misleading, or false notion, belief, etc.: That the world is flat was at one time a popular fallacy.
(b) a misleading or unsound argument.
(c) deceptive, misleading, or false nature; erroneousness.
(d) Logic. any of various types of erroneous reasoning that render arguments logically unsound.
[1] to paraphrase "The Princess Bride"