If you forfeit, your opponent gets the following minutes:
Starter = 36 minutes
Backup = 10 minutes
Reserve = 2 minutes
If any player is set as the starter and backup at a position, he only gets 41 minutes total (5 minute penalty for starter + backup -> 36 + 10 - 5 = 41)
If any player is set as the starter, backup, and reserve at a position, he only gets 43 minutes total (36 + 10 + 2 - 5 = 43)
If any player is set as the starter and reserve at a position, he gets 38 minutes total (36 + 2 = 38).
I'm not sure what happens if a player is set at starter and backup at one position and backup at another, but for single position training, that doesn't really matter.
Common courtesy would dictate that if you intend to submit a WO lineup, you pre-notify your opponent, so he can adjust his lineup if he wants.
In addition to not getting training minutes, you also won't get any benefit from TIE on a game you walkover (so you'll be in an enthusiasm hole compared to actually playing & TIEing the game).
BB-Charles has often maintained that finishing higher in the league standings will more than offset the short term "economic loss" of having to pay the week of salaries while you get curbstomped in the first playoff round.