Gee.....does that mean all these years and Zillions of flight hours....the Yanks have done it all wrong? You have any accident statistics that would prove your point?
Are US Accident rates higher than the UK for such a reason?
Surely you know of what you speak so you should be able to corroborate that or you would not be saying what you are.
I have not flown out of my home airport in probably thirty years but I still remember the Field Elevation is 960 feet. How hard is the Math(s) to keep track of your cardinal heights which in our case were 400 feet and 800 feet.
Even if I merely rounded up to 1000 Feet and then added my numbers, would it really make a damn?
Considering acceptable Altimeter Instrument error is 70 feet plus or minus, and some variation in actual Barometric Pressure due to normal pressure changes between recordings, just how accurate does one need to be in the math(s)?
What tolerance do you demand in determining a height at which you will turn back or not? One foot....Ten Feet....a Hundred Feet....Five Hundred Feet?
Is it the Altimeter Indication that is your final factor or your Mark I Eyeball and Brain working in conjunction with each other that is the final bit of information that facilitates that decision?