It is incredible that people claiming such high experience - as a captain! - can totally misunderstand the physics of flight so badly.
Of course you're right, but just for nerdly kicks I went to my calculator to answer an old question: If the centerline of the fuselage is in a perfectly coordinated turn, what's going on at the wingtips? The outer wingtip is travelling further in the same amount of time, and seeing higher airspeed. But it's in a slightly wider turn, too. Do the two cancel out? Is the outer wingtip overbanked or underbanked?
Could it possibly be that while Bob Hoover's coffee in the cockpit pours straight down into his cup, the fuel in his tip tanks is sloshed towards the outside or the inside of the turn? (Answer: Yes, but by such a silly small amount that you'd have a hard time measuring it)
Figure a 30 degree banked turn at 200 knots, which ought to give a turn of radius 6153 feet, a little more than a mile. ((I used v squared / 11.26 * tan(bank angle). Figure a 100 foot wingspan, and accounting for the bank, the outside wingtip travels in a circle of r= 6196 feet, covering more distance in the same time as the fuselage, and the inside travels in a circle of r= 6110 feet. The inside wingtip is seeing airspeed only 99% of what the fuselage is seeing, and the outer wingtip is seeing airspeed of 101% of what the fuselage is seeing. The perfectly coordinated bank angle for the outer wingtip would be 30.2 degrees, and the perfectly coordinated bank angle for the inner wingtip would be 29.8. Nobody can tell the difference of 0.4 degrees, and it's certainly not going to slosh any fuel around.
Run the same numbers in a 60 foot wingspan glider circling in a 45 degree bank at 50 knots, and you get almost a 10 degree difference between the apparent gravitational "down" at the inner wingtip vs the outer. Not enough to spill Bob Hoover's coffee, but measurable.