I would actually have to look up the GM advice and see what it actually says, but in my memory it says the GM decides whether a roll is called for, even in combat.Do the rules encourage the GM to roll for it in the case of sword play, regardless of the difference in skill level, because combat is (apparently) so central to the game?
5e has two toggles right now - contested so the schlub has a decent chance of winning against the GOAT, and uncontested where the GOAT just wins. I just find myself wondering sometimes if having one extra level of randomness in the middle would help.
What D&D needs, I think, is more explicit nonbinary outcomes in resolutions: success at a cost, complications, partial successes and failing forward. The DMG mentions these briefly but there is little actual support or advice.
I want to expound on the idea of not giving the novice swordsman a chance against the master. It sounds wrong at first because fighting is so central to the game and players often feel there should always be a chance. In this case, the point isn't a fight. There is some other narrative purpose behind presenting the PCs with this master swordsman. It could be anything from.establishing a villain to world building to foreshadowing a future duel. In any case, it isn't a "challenge" and therefore the PCs don't get a check (or a fight).