It is surprising but if you pump the spare up to say 30 psi you can see the gap close as the tyre expands lightly. I was testing / playing with my new rechargeable tyre inflator at the time.
But they also make different lengths of the shank. I bought used a cobra head from a 4/4 to see if I could make a brake light out of it for when the suitcase covered the existing cobra. The shank was shorter than my S1 Roadsters one. I assume to accomodate narrower tyres.
