It is not a grey area. (but what others are there?)
All new M3W are now tested to MSVA (Motorcycle Single Vehicle Approval) as the earlier models' Type Approval Certificate is no longer valid as the design has changed so much. The MSVA is a 'cutdown' form of the Type Approval requirements, but it is still an intensive 4 hour test.
To pass the MSVA the M3W needs front mudguards. If you then remove them that is an offence, as it is illegal to have parts on the vehicle for the MSVA (or IVA for cars) just to pass the test and for them to be removed afterwards where if they had not been on for the test the vehicle would have failed.
It is interesting as the M3Ws that are presented for MSVA have a plastic dish over the octagonal wheel nut to meet MSVA as the octagonal nut will not meet the requirements. If you look at the photos in the M3W parts book from the factory you will see a photo of the M3W front wheel with the plastic dish fitted.https://assets.publishing.service.g...e-vehicle-approval-inspection-manual.pdf
... Any part of the wheel must not project more than 30mm beyond the body (Mudguard is part of the body) and even then must have a radius of <30mm, so the octagonal wheel nut on M3W will not meet that.
I had to get my new unregistered Buckland B3 through MSVA and so had the opportunity for a chat with the DVSA inspector, he has done so many M3W in both Exeter and Bristol, hence a longer waiting list than a few years ago for the three wheelers!
Hope that helps, cheers Peter.