Hey Slim,
Because the part of the rendering that WokenfromJWCult and others object to is the “exercising” part, not the “faith/trust” part, which you have missed.
I actually understand better than most why the word "exercising" is objectionable. WokenfromJWCult appears to be paraphrasing Robert Bowman so I understand where the argument comes from as well.
The word I am objecting to is "mistranslation", which would be a violation of the rules grammar and definition
The only time πιστεύω needs to be translated as believe/believes/believing is when it is followed by a dative noun.
When it is followed by a preposition like εἰς or ἐπὶ it means more than simple belief and the translator is free to pick an equivalent English expression.
The word "Faith" in English is a noun which requires a verb to function properly. "Exercising" is a weird choice when there are simpler verbs like "Have", "Put" and "Place" that can be used, but that is a theological, not a grammatical debate.
Narkissos (As you point out) called this "overtranslation"