Strat-O-Matic Baseball 365

Happy to have a walkoff pinch hit homerun by my backup catcher, but not sure why the move was made.2009U set league.Tie game bottom of 9th. Coste pinch hits for Todd Helton.
https://365.strat-o-matic.com/game/463393/1820
BOTTOM OF INNING 9
SUBSTITUTION at P: Ramon Troncoso (R) (role: RH Specialist)
0 J.Carroll 4-7 Strike Out b-0 F9
1 Y.Escobar 1-9 Single (CF) b-1 F9
SUBSTITUTION at P: Jose Mijares (L) (role: LH Specialist)
SUBSTITUTION at PH: Chris Coste (R)
1 1 C.Coste 3-9 Home Run (CF) 1-H b-H F9

Pros
Coste bats righty while Helton is a lefty
Helton is "w" against lefties

Cons
Helton's card still much better against lefties than Coste plus has a HR chance
This advantage in Helton's card over Coste appears greater than the difference in Mijares card's split.
There is a runner on base so a homerun is not needed to win.

https://365.strat-o-matic.com/team/leftright/1711582

Maybe it makes perfect sense. Am I wrong or missing something here?

I never understood Hal's pinch-hitting methodology, but he seems to have good judgment. Helton is the overall better batter, but Coste is N powered against lefties and has a few home runs on his card.