Quick Grunfeld Question

The followed position was in a game I played. My opponent played 12. d5, which I cannot find any games on. Why is d5 only played after 12. Bf4 Qd7 13. d5?

How should black "punish" (if anything) White for playing such a move?

13... Ne5 and if B/c4 is moved or protected 14... Ng4  and white has problems

Looks very dangerous. But how about 13. Bf4 pinning the knight? And if 13...Qd7 this looks like mainline 12. Bf4 except the knight is on e4 instead of a5. Or is something like 13...g5 14. Bxg5 Ng4 15. Bf4 Be5 quite strong? Is there some other better lines?

Edit: It seems like I missed that the bishop can't do 14. Bxg5 because of 14...Nxc4 so after 15. Bg3 does black follow up with something like 15...h5?

After 14 Bf4  Qa5 has scored well for black, 14.... g5 is too loose/weakening/risky

after Ne5 your giving their knight a very good outpost along with hitting your bishop with a tempo...in the openings, you shouldn't be giving up tempo like that

So... to punish d5, simply Ne5 , hitting the bishop with tempo is best

Ah looks very good. Putting lots of pressure on the c3 pawn (especially with the open dark-squared long diagonal). Also I think it forces white to trade the light-squared bishop for the knight (if black wants). Thanks.