lets assume we have 10 products
each product has different variations (lets say five on each caracteristic)
when you add a caracteristic products->caracteristics you add for example the title "Measurement" and valuse "1mm","2mm","3mm" for the first product and "3mm", "9mm", "20mm" for the next product and the same goes for the next caracteristic and so on you get at the end a useless amount of variations on the product page when calling all the carateristics!
I had for example added 4 caracteristics on a product and the "manage variations" gave 160 variations!!
But the product had only 5 different variations. Just because other products had "Measurement" caracteristics it added them all up in that product and made variations of them as well.
If you could choose the applying caracteristics like the custom fileds which have multiple dropdown the automated creation of variations would be narrowed to these values!
The problem is that you have to delete manually the wrong variations and since we are talking about numbers and codes it is easy to delete accidantly a right variation.