Well Kodak Ltd were selling some largercameras with spring backs before WWI here in the UK. however the U5x4 Premosold in the US took a standard fit DDS spring back but those sold in the UK had a bookform back. I have a Premo 5x4 DDS in front of me it is interchangeable with a modern DDS the onlt difference is the light trap area is much shorter and the other end doesn't fold over to hold the plate instead it has a sprung piece inside. I also have an Eastman Kodak 5x4 plate holder same fit but the plate sits slightly more towards the end away from the light trap it, lists EK patents 1904, 1906, &1908, so there still wasn't an absolute standard at Eastman Kodak as tehy owned Premo.
I ssuspect the spring back and more modern style DDS were introduced to UK photographers by US troops during WW1, I'm not sure when Kodak Ltd began making field cameras here in the UK but that's the point when British made spring backs seem to have appeared here.
WW1 had a big impact on the photographic industry here, a shortage of specialist optical glass had lead to the Government getting Pilkingtons to enter the market, and they are now the world leader in specialist optical glass. Another change was British made cameras all used mainly British lenses, Kodak Ltd in particular was making almost all cameras for the British and Continetal market in the UK and using British lenses but then they had strong links with Ross who they weer agents for in Australia and New Zealand and Cooke who Eastman Kodak distributed in the US and Canada for a while.
I've not seen a reference to a spring back in any BJP Almanac before the end of WWII except with Korona Banquet cameras imported by Kodak and a Kodak Ltd Wide Angle whole plate camera. I'm only missing one BJP Almanac from 1920-63 I think 1925.
It's probable the back you have was a special order someone who appreciated the Kodak Plate holders they were selling in the UK. It's odd that the spring back and it's greater flexibility didn't become standard here until after WWII.
Ian