Tie games are NOT included in the as played schedules because they do not count in the standings; they are ignored when calculating winning percentage. Also, tie games were treated like postponed games in that they were (usually) replayed in full. If you add the tie games back into the as played schedules teams will be playing too many games since OOTP cannot force what were ties in real to be ties in the sim.
Take 1915 as an example. Cincinnati had a record of 71-83-6 that season. It had 154 games played to a decision (win or loss), the number of scheduled games in the schedule. That means all 6 of those tie games were replayed, and to a decision. If you put the tie games into the as played schedule Cincinnati will be playing 160 games to a decision in the OOTP sim since there is no way to guarantee those 6 games end as a tie in the sim.
Note that it isn't just tie games, there are also 'no decision' games which were sometimes counted in the player statistics even though the game result was wiped from the standings. See this page at Retrosheet for more:
No Decision Games