@Design team, how does talon's E works?

The jump attempts to place Talon at the point he targets, but there is a limit to the raw distance he can jump. If you attempt a jump that surpasses that limit, then you'll get placed at the nearest possible point that you could legally jump to.

Because this guy tried to jump over a huge section of terrain, the only place the jump could actually go was along the small curve on the wall. Anything else would have been too far.

I have played it extensively and to break it down in the most straightforward way possible.

Talon's E is a Wall targeted Dash that has a set range. (The range can be seen when casting the spell with the indicators.

Talon can Leap to any point around the wall he is touching if it is within said range indicator.