I'd rather the reserving be removed for legendaries in general. To reserve means to ensure, what you describe is closer to "setting up a chance", since it isn't guaranteed that you will catch it, nor does it stop someone else from trying if they also want it. I mean if someone happens to catch it before you who 'reserved' it, then it would defeat the purpose of a reservation in the first place.

Basically I believe you phrased it wrong.