Yeah, that's my bad, if I'd dug deeper into the function I'd have realised that the code is checking that you can exit the tile in the direction that you are facing and that you can enter the tile in front. There are alternatives that might be safer.
JavaScript:
var space = 2; // tiles to move, change number to increase/decrease distance.
var d = $gamePlayer.direction();
var x = $gamePlayer.x + (d === 4 ? -space : (d === 6 ? space : 0)); //adjust x if facing left or right.
var y = $gamePlayer.y + (d === 8 ? -space : (d === 2 ? space : 0)); //adjust y if facing up or down.
var passable = $gameMap.isPassable(x, y, d);
$gameSwitches.setValue(id, passable); //replace id with switch id to use in conditional branch.
So long as the tile being landed on has passability in the direction the player is facing, this won't trigger the else branch. No checks are done on the tile in front of the player's landing position.
If you're going to be having the player land on tiles that themselves have limited passability it might be worth checking to see if there is Any passibility by doing some extra checks.
JavaScript:
var space = 2; // tiles to move, change number to increase/decrease distance.
var d = $gamePlayer.direction();
var x = $gamePlayer.x + (d === 4 ? -space : (d === 6 ? space : 0)); //adjust x if facing left or right.
var y = $gamePlayer.y + (d === 8 ? -space : (d === 2 ? space : 0)); //adjust y if facing up or down.
var passable = $gameMap.isPassable(x, y, 2) || $gameMap.isPassable(x, y, 4) || $gameMap.isPassable(x, y, 6) || $gameMap.isPassable(x, y, 8);
$gameSwitches.setValue(id, passable); //replace id with switch id to use in conditional branch.
While this is not so nice to look at it checks for passability in all directions and if there's at least one then it's fine to land on the tile. Again, this doesn't check any of the neighbouring tiles.
If you wanted the player to at least have some wiggle room when they jumped you could replace "$gameMap.isPassable" with "$gamePlayer.isMapPassable" and it will only execute if the player can enter a space and make a move in at least one direction. I'd argue that this is unnecessary though as the player can always turn around on one tile and reactivate the ability - if they want to jump into tiny holes who are you to stop them?