the cable boss is an integral part of teh structure of the bike, without it, the welds tend to fold in on themselves, not just breaking the bike (obviously) but also creating a razor sharp edge to the top tube which slices through skin like butter. Apparently the sharpness is part of the construction techique, where they hand roll the tubes in halifax instead of using regulation pipes like generic far eastern companies. This is part of teh allure of a handmade in yorkshire bike.
Interestingly, using a full length gear outer has also been shown to reduce low speed suspension response on technical stone based trails (not applicable in the mud), though with current changes to trail substance at trail centres and popular bridleways this is less of an issue.
Or not, I’m sure its fine, but sometimes shifting suffers a bit, though its less of a problem for front than back.