I get those wall clings pretty often when looking for wall jumps. I don't understand what the situation is where I would ever really want to wall cling. Hate it.
And it is really hard to aim Greninja's up B in time. That move is quick, but the circle pad is not.
More often than that stuff though, I tend to side B instead of up B. Greninja can live through it, but barely.
The wall cling really baffles me, of all the mechanics they introduced in Brawl and chose to keep it was possibly the
least useful and most intrusive one to a character's gameplay. I would automatically trade wall clinging for swimming, at least the latter I could avoid completely by not playing on the stages that have water -- the former I can't avoid no matter what I do.
A lot of it has to do with how they programmed wall clinging. Not only is it because it goes into the wall cling if you hold towards the stage for X seconds (this is why it's really easy to do accidentally because if you're drifting towards the ledge it's likely to read that as a wall cling and take priority over the ledgegrab), it doesn't let go
unless you jump or input away from the stage. That is the most backwards way to go about it. If you wall cling and let go of the stick, you should
fall. Not get stuck on the wall until the timer for the wall cling runs out or until you press a different input.
Of all the things they could have removed or changed, they chose to do nothing about wall clinging and just kept it as though it was an integral aspect to any character's gameplay (when really it wasn't and still isn't integral let alone useful). I don't even remember anyone using wall clings in competitive Brawl for their intended purpose (Lucario's Up B into wall cling or Diddy's Side B to wall cling don't count), they just get in the wayyyy!