Unfortunately, allowing this strict RAW
ruling allows for some rather shadey stuff to happen so its better to say that it doesnt work.
You break the rules when you say that it doesnt work. GW
has clearly shown in their FAQ
that its intended that a unit coming in from deepstrike can have a shorter charge, when there is vertical distance involved.
From Warhammer Community
, updated 2 June 2021:
Due to some quirky interactions with vertical distances (and some fascinating Pythagorean loopholes), certain units and Vehicles could be charged easier than others by units arriving from teleportation chambers or other similar rules.
As much as we’re fond of bringing ancient geometry to our tabletop battles, it didn’t treat all models fairly. To ensure there’s a level playing field the Studio team have clarified these distances. Now, you’ll always have to make that 9” charge to reach your foe on the turn you arrive.
I haven't seen it in the official FAQ
yet but the way they write it in the article makes it sound like you can deep strike any were and as long as you are in charge range all it will take is rolling a 9.