Like others, I learned to preflight the aircraft from day one, and accepted that as my own responsibility. The instructor always took my word for it, and this goes for helis, gliders and power planes. So I understood from day one that it was my word, even as a newbie, that kept us alive, and made doubly-sure that all was kosher. Transitioning to solos was trivial in this respect, since I had been "Preflighter in Command" from day two. My CFI (in all those categories and many different flight schools) never helped me preflight after the first lesson, and come to think of it, all my DPE's have trusted me with it too.
So to imply that the CFI, beyond the very first lesson, has any role (except perhaps a very casual and random one) in the preflight (or fuel checking which is part of it) is simply wrong, based on my very broad experience over many schools and aircraft categories. And as I mentioned above, if that implication were to become the norm, it would lead to a worse safety record.