You really need to remember the bandplan for UK stations is advisory and not compulsory. In general, bandplans help people by trying segregate modes that don't make happy bedfellows. They also give suggestions to where certain modes can be found. And that is about that. If I want to run FM on 14.100 MHz over the top of the International Beacon Project there is nothing anyone can do. Sure I would not be popular nor receive the support of my peers but it would be legal. You could claim I was interfering with the beacons and I'd say I opened the squelch on my receiver and listened for 1 whole IBP cycle and heard nothing a suggesting the frequency was in use. I'd be clear to continue. But not popular.
In this case, the wording is a suggestion that UK stations should go somewhere else for inter-UK operation. That's a reasonable suggestion, we have lots of spectrum compared to some people. Having inter-UK QSOs and blocking the WRC chunks that overlap is somewhat selfish if we can go elsewhere. Normally we can go somewhere else.
But what if all the frequencies are in use? There are 2 weekends in March when there will be lots of Cadet operations on the old FA,FB etc. channels so I may find a distinct lack of free space if amateurs move to other frequencies instead of the old NOV channels. Well I can avoid the WRC overlaps most of the time if I don't want to specifically work outside of the UK. But when the band is busy it's not possible to avoid using spectrum that is allocated to me.
The footnote reads fine to me, it's a suggestion to help organise activity so more of us can use a shared and limited resource. It would be sensible if the overlapping freqs were given. The expression "if possible" is nice allowing a degree of flexibility and accommodation. Sometimes it's not best to have every T crossed and I dotted. You get to use your skill and judgement as a responsible adult and not blindly follow orders.