Spur don't play basketball, they play Pop Ball.
I doubt Pop has ever told a Spurs team to just go out and "play basketball".
No grind it out, no creative free-lancing, everything by the Pop Rules and Pop System. It obviously works most the time, but the disadvantages are the the players can have a hard time, for fear of violating the system, of being creative when the system, not perfect, encounters difficulties posed by the opponent. Some people think Pop seems to have a hard time making in-game adaptations, from diverging from his game plan. But I think the bigger factor is not Pop system, but the team "having bad games", esp on the road, where they can't figure out a way to win in spite of having a bad game.
For the road vs home discrepancy, nearly all teams in all sports play better at home than on the road, but the best teams manage to play nearly as well away as at home.
The 04 Spurs weren't a very good road team, and lost 3 of 4 games to the Lakers @Staples.
The 05 Spurs aren't a very good road team compared to other top teams in the WC (only 5th) and worse in the league (only 7th).
That's why dropping Denver Game1 @SBC was so disastrous. The Spurs were supposed win all the home playoff games to match/exploit their league-best dominance @home, then play .500 ball, split, on the road. Spurs win the series. The Denver series worked out ok.
But the Seattle series hasn't, as the Spurs weren't able to get the split @SEA, so now we're back to a starting new series, of 3-games. If the Spurs hold serve, they win, but it sure would be nice to finish the series with Game6 @SEA.