It could well be. What I couldn't understand when my car stopped with a dead ITP was that putting 5 litres of fuel in didn't get it going but 15 litres did. Adding 5 litres would easily immerse the inlet to the ITP, so it had to be something else.
I remember having some lively discussions with TC over on the dark side when we were trying to get to the bottom of what was happening.
Thought at the time that the fuel was drawn from the other side of the saddle, so needed to put in more fuel to get it over the saddle, but now I think that when the tank level gets down to the priming valve then adding 5 litres may not be enough to cover it again as the cross section area of the tank at that height is quite large. Only guessing but it could make sense.
Mike