Hard to say of course, but my sensation of long-run glycogen depletion (that Maurten massively changed), was a wearing down of the soft tissues in the legs (quads, hip flexors, etc). Very different from feeling like I had aerobically “run out of fuel”. So to me, what you describe almost sounds similar, but who knows.
Having possibly come across as criticising you above, I actually did very similar on my long run on Sunday. I had a proper breakfast, but then did 30k, with no water (it was hot) and one gel just before my first 20min IM MP effort at 85mins in, and another in the 5min recovery before a second 20mins. My legs afterwards were a mess. I had nothing in them, and stairs were a struggle for the next 24hrs due to things like hip flexors etc not being happy. I put that down to fuelling.