In the following game against Fritz 10, Black played very aggressively but wound up in a Queen and pawn endgame where White was guaranteed of an outside passed pawn. White gets to open an extra file so the piece play favors White even more than the Smith-Morra Gambit.

7...exd5

8...Bc5

9...Be7

What in blazes does this have to do with the Smith-Morra Gambit anyway?

How is 6. ...d6 "too passive"?

It's just a regular Scheveningen setup, except White has played a useless c3 blocking the natural Nc3. If White wants to control b4, he should just play a3.

So why on earth Black would ever enter that line at all is beyond me, he needs to be very careful when playing d5 and as you've shown here d5 is a bad move in this line, which would be equal or good or for black if he played d6 as normal.

lol.

I found exactly one instance of 6. c3 in 365chess.com of the masters section out of the nearly half a million master games. 

http://www.365chess.com/opening.php?m=11&n=1444&ms=e4.c5.Nf3.e6.d4.cxd4.Nxd4.Nf6.Bd3.Nc6&ns=3.3.4.75.131.143.132.704.1356.1444

Black's next move was d6, White lost.

Also, I think you mean "transposition to a favourable variation of the Smith Morra", not a "favourable transposition". You are not comparing different transpositions with the goal of reaching the same position here.

Here is a game I played against Fritz 10 at 240'40. Black is in zugzwang by move 9. There is no way he can improve his position.

Does taking the queen not improve his position?

I'm starting to get the genuine impression that sloughterchess is a joke account.