This is not about whether the team will make the playoffs or not, rather it is an attempt to rank them by a statistical measure to establish some objectivity about the team, beyond the win/loss record.
I personally have always used the scoring differential, that is the difference between the teams average score per game vs. how much they concede to the other team. Over time I have observed that the teams who win by the largest margin game in and out are the best, and the NBA champion is quite often the one with the best point differential.
Although a good predictor, it isn't perfect, and I didn't expect it to be. Some teams rest their players more, their eyes on the playoffs. The data comes from play against all teams, not just the playoff-bound ones.
Right now the Sixers are 1-4, only 5 games into the season, so the statistical sample is small. The NBA.com page allows you to see all the teams and make comparisons based on the difference between their offensive and defensive performance. Based on these numbers the Sixers are about 15th in the league, having a negative score of .20 points per game. A score of 0 would mean they were a .500 team so they are really very close.
The team continues to improve game over game, and it seems likely that this will start to translate into wins. Even though they aren't built to compete, a lot of other teams have even worse flaws, and the Sixers will play them about as often as they do teams that are more complete.
Right now, the trend for the Sixers is up. They are playing and competing like a team. The concern is what is their true potential given who they have. They appear close to being a playoff team to me, and I expect that to start to show up in the win column.