Of course it'll work!
The link kindly supplied by Zeezeebaba states the zone is must not foul is in the SWEPT area of the windscreen. If the wipers do not touch it, it's not a swept area. If it's not a swept area, you can have what you like there. As long as it gives "the driver an adequate view of the road" (their words, not mine) then smaller wipers are fine.
Trust me, I'm as picky as anyone, but this is absolutely fine and a genuine workaround. Or you find an MOT place that has half a brain.