I first thought that the new movement system is more realistic. But it's not.
Sure, in CivV it was quite weird that a unit with just 1 movement point left could with no problems climb a hill requiring 2 movement points. While some other unit with 2 movement points left would be able to do exactly the same thing and nothing more.
But in CivVI there are other problems. A unit with 2 movement points moves towards a hill and has 1 point left ... and cannot do anything at all. He still has movement points, but cannot move at all, not even half the hill.
How to implement it the most realistic way? This question is very stupid in fact, because Civ is a turn-based game with discrete movement distances (tiles), so nothing will be realistic. But it would be more logical if for example the game remembered remaining movement points and transfered them to the next turn.
So - you approach a hill with only 1 MP left and you give order to enter the hill. The unit will stay where it was (cos it doesn't have enought points to climb the hill), but the game remembers that it has one point left. Next turn it will finish the climb, the unit will appear on the hill tile, but will still have 1 MP remaining, because it used 2 out of 3.
But I wouldn't allow to reserve points by intentionally skipping the turn, you would have to finish the move. Not something like moving 1 tile on a flat land, hitting skip turn and the next turn being able to move 3 flat tiles.
In other words - the game would internally allow the unit to end "in the middle of a move" - for example in the "middle of the hill slope, half the way up".