Below is the text of a ticket I just submitted to WG. If you also feel that this WG practice is inappropriate, you might add your voice to the issue.
"I recently learned on the forum that WG has instituted bots on the SA Server due to low population usage and that battles fought against bots are being factored into Ace mastery calculations on both the SA and NA servers for tanks of Tier V and below.
We went through this once before when Proving Ground battles against bots were being factored into Ace Mastery calculations. WG realized that this was unfair and changed it.
Now, however, it appears that WG has repeated the mistake on a much larger scale. I encourage you to correct the issue since battles against bots grossly skew Ace Mastery calculations."