no, think of it like this, you go on a long journey or use your brakes a bit then you pull on to the drive park up and put the handbrake on. If the disc is wet it then dries wuite quickly and this causes it to slightly stick. Its just the pad sticking to the Disc thats all.
If you remmeber a few years ago xantias had a
problem with parking on hills due to a front wheel handbrake, it was due to the front discs being so hot when they parked up, that after a while the disc would reduce in size due to cooling meaning the handbrake at the front slipped and thus car rolled sown hill.
Not so much the case in the
ibiza as rear discs should never get a shot as the fronts. But this is how the sticking comes about, water evaporating leaving crap between the pad and disc causing it to initially stick. if its only occasionaly in the wet then theres nothing to worry about, if its all the time get it checked. Also depends how hard you pull the handbrake up, if like brother that means untl the lever hits the cieling that will alos accentuate the sticking.