One could always request a ruling from the DVLA but perhaps it is best to let sleeping dogs lie.
Please! We are currently protesting the recent rule change for driving licences and the omission of the front plate 'because it is a motorcycle' does not sit well with the argument that it isn't a bike, and a bike test is an irrelevance and one should be able to drive it with a car test pass at 17. Not two bike tests and experience and be a minimum of 21.
My MP has put the question to Minister of Transport, but I've not yet had an answer from there, or Greg Knight MP who is the chairman of the All Party Historic Vehicle Group. I have suggested that DVLA redefine car bodied three wheelers as cars to get over this. A front numberplate is a very small cost.