We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "michael adams"
saying something like:

Having got home, I thought I'd try connecting the set up to the garden hose
using a spare flexible tap connector, and the cold tap seems to work o.k
despite the obstruction. So maybe there's supposed to be an obstruction
there on the cold water side. Dunno.

The cold kitchen tap is mains connected and the hot is normally (still,
in most houses) tank fed. A built-in restrictor on the cold feed makes
sense. Unlike the Froggies, who tend to have equal pressure kitchen
mixers, more suitable for a pressurised hot and cold, or equally low
pressures, if needed.
It'll probably be ok.