The only reason aircraft have approach idle (or high idle or whatever it's called) is to meet the 8 second certification requirement. It could obviously not be achieved from a normal (ground) idle, so higher idle setting is introduced so to achieve full rated thrust in 8 seconds.
Stabilization criteria is up to the company, as long as it is acceptable to the relevant authority. Some Airbus operators indeed have SOP where you can be stabilized with idle thrust, as long as other parameters are within limits.