'Upgrading' to skinny tyres pointless for London commuting

I gave this a little try out this morning as I had to pump my tyres up anyway. I'd always been a 100psi man for training rides and 120psi for races, not for any particular reason just experience of what I like. It never occurred to me that different front and rear psi's might be worth trying.

At my weight (79kg, 90 with bike and kit) the calculator recommended about 120psi in the rear and about 90 in the front. Which is all on the huge assumption that my weight is distributed 60% over the rear wheel.

I can report that todays fast, spinny, fixed training ride in Essex was not only one of the most comfortable rides I've had on that route but the bike handled just a tiny bit better than it usually does and everything was blissful.

How did you eliminate expectation bias?