I’ve been thinking about this, and I don’t think you are correct. Illegitimate totality transfer is about saying all the available senses of a word apply to a single use in context, which violates the basic principle of language that (unless you are intentionally making a pun) only once sense of a word can apply for each use. So if I say, “the chicken is spoiled” I can’t be talking about both the temperament of an animal and the freshness of its meat at the same time. Context will determine which sense of the word spoiled I meant.
Pistis is used 227 times in the NT with the following available senses; 1) faith, trust, belief; 2) the Christian faith; 3) conviction, good conscience; 4) doctrine; 5) assurance, proof; 6) promise
The idea of faithfulness is part of the semantic content of sense #1, hence the ongoing debate about the best translation of pistis christou in English. (You can google it to read all about it.) Is it “faith in Christ” or “the faithfulness of Christ”? When you combine the ambiguity of the Greek genitive with the fact that the first sense of pistis includes the idea of both trust and faithfulness, context doesn’t give a clear indication of what would be the best English rendering. This is not a matter of deciding which sense of the word pistis is being used (we know it’s the first one), it’s about what the best translation would be in English.
What @DennisVenema is maybe trying to get at is not really about the semantic range of pistis (which can be used in the sense of faith/trust, Christian faith, conviction, proof, or promise) but about the semantic content of the word pistis when it is used in the sense of ‘faith.’ The semantic content of the use of pistis that we would typically translate ‘faith’ or ‘trust’ in English has more depth than the semantic content of those English words.
If I translate murder to matar in Spanish, I might lose some depth of semantic content, because murder in English includes the semantic content of intentionality and violence, whereas matar just means to kill.
Translation always involves dealing with these kinds of semantic mismatches.
It is correct to say that faith does not capture the depth of the semantic content of the Greek pistis because there is not a perfect semantic overlap between the two languages. The Greek word, when used in the sense of ‘faith, trust, belief,’ has the semantic content of loyalty/faithfulness as well. To acknowledge this is not the same thing as claiming that the entire semantic range (all the available senses) of pistis applies in a single use, which is what illegitimate totality transfer is all about.