You're not crazy.
Matter of fact, when someone tells me, "It only does it when the fuel tank gets below a quarter," I don't dismiss it. I get interested.
Over the years I've learned that the vehicle doesn't care whether the symptom sounds logical. If it happens consistently under the same condition, there's usually a reason.
I've seen weak fuel pumps that couldn't stay submerged once the fuel level dropped. I've seen cracked pickup tubes inside the tank that started sucking air below a certain level. I've seen debris in the tank move around and partially block the pickup only when the fuel got low.
Now, does that mean your transmission is actually failing? Not necessarily.
Remember, the transmission can only transfer the power the engine produces. If the engine is starving for fuel for a few seconds, it can feel exactly like a slipping transmission.
That's why I always ask, "Is the transmission acting up...or is the engine losing power?" Those are two very different problems that can feel almost identical from the driver's seat.
So no, I wouldn't call that impossible. I'd call it a clue.
One thing I've learned after almost 40 years in this business is this:
The weirdest symptoms are often the biggest clues.
The trick is not ignoring them because they don't fit what "should" happen. That's usually where the diagnosis starts.