Calling Shanto for the practice is ok. However, if he makes it in the final 15, that will be sad.
As for picking Talha over Anwar, my guess is, those idiots are probably using quota to select players. 12 from last series, 4 from previous drop outs and 4 from dhaka league performers, something like that.
Otherwise, there is not sane reason to call Anwar over Talha who is not injured.