There are regular season teams and then there are playoff teams. And there are often differences. In fact, in the East Boston is the only team I'd have in the top 4 for each (and they are 1 in both).
Regular season
Boston, Orlando, New York, Cleveland
Post season
Boston, Milwaukee, Miami, Philly (with Embiid)
To win in each requires different things. To win in the playoffs you need a top level reliable player and you just don't need that in the regular season where quality depth is far more important to winning. Take the Cavs, they have a bunch of really good players and very solid overall depth, but they don't have a top 15 player to take over when you need him to in the playoffs. The depth has allowed them to withstand injuries and win at a good level in the regular season, but they aren't a deep playoff contender. And conversely a team like the Bucks can look like a train wreck at times in the regular season, but when push comes to shove they have 2 top level players they can rely on to finish games.