Depends on what you're doing. If you're in a steap dive, such as near-vertical, then acceleration and lack of altitude is doing it. If you're in a very shallow dive, then yes, it's just a matter of not having enough fuel in the tank. Which is basically what I said.

Also, don't discount the amount of time it takes the fuel to go through the lines, and the fact that a single bubble won't usually be noticeable. (you can test this by pinching off the fuel line when the engine is running and time the amount of time until it dies, probably a couple of seconds. Figure out how high you have to be to avoid hitting the ground in a dive for that many seconds).

Anyway, the agree on the main point that the clunk doesn't move to the front of the tank in a dive, and it doesn't matter that it doesn't.