Of course it is, but I think it would have been better do to GP2 or FR 3,5 rather than not to race for one year and do just one test session / race weekend. We can see what happened to Maldonado and Grosjean who were GP2 champions and still made dumb moves when they were actually racing in Formula 1 and that is why I think every driver nowdays should have a path or a minimum number of races completed in this support series in order to get into Formula 1 as a main driver.
Apparently Williams management believes that driving the car on fridays prepares him better for F1 than a GP2 season.
Maybe this way they can see how fast he is in comparison to their regular drivers or something...
Bottas was a Williams driver before 2012, they could've easily found him a good place in GP2 if they thought it was the best decision.