When Morgan build their cars they add little titbits of charm into the design. Odd sizes like that are in the apprentice training manual.
Also, they set the cars up with Malvern air in the tyres. This finely tunes that suspension component provided by the tyres/pressure. Topping up elsewhere can lead to changes......

The more you work on your Morgan the more of these charm additions you come across!
Welcome to the world of Morgan tinkering! It adds to the ownership enjoyment.