your math is incorrect, the probabilities are independent from each other, its a fact. what you wrote is probability to get level 10 when every previous enchantment is dependent on the next one.
yes its questionable how you can get level 10 in less than 2 years with this restoration policy, not so questionable to get level 9 though, level 10 is around 13 tries from 9 to 10.
Until level 9, well, its a pure luck, i made level 8 from 2 tries the first one broke on level 3 so what?
probably there was an abuse, i do not argue with that, but it is possible to get 10, and eventually everyone will get it, not so fast though.