I don't really see anything "spoiler" like in providing total amount of practice needed for the next level. You can find out needed amount of progression points, so why not practice as well. But having the explicit message with points gained for some action is the minimal convenience that is lacking now.
Purely using visual progress bar is not useful as Bilbous pointed out, since it often can take you many actions until you'll see some movement in that progress bar, and you still have no idea how useful or helpful those actions were. The worst example was the case when magic rules were being updated, and practice was set to very slow pace after the first update. One had to cast some spell more than 30 times to see the progress. It was easy to assume something was simply bugged and broken, while seeing actual practice gain and total amount needed could right away point out the problem (that progress pace was set to extremely slow), and help report the issue and save developers and users unneeded frustration.