+1 on all that's said above, it's a good common-sense safety practice. Think of it this way: when the gun is cocked, the "tension" from the mainspring is NOT GONE! It is in fact at its max, but has moved from your cocking hand to the tiny parts in the trigger mechanism. Those can fail, turning barrel-cockers and sliding-breech fixed-barrel guns into little guillotines.
I learned this lesson the hard way, many years ago when a top-lever cocking air pistol "bear trapped" on me. I got three black fingernails and a broken bone in one fingertip (and, I was actually lucky three fingers were in the way - had it been only one, the tip would probably be gone). And any springer rifle is much more powerful than that.