You could argue the other way, those teams, especially 9 and 10 seeds far behind 7 and 8, have already proven themselves to be average or terrible over a whole season. So what is really the point of that?
But I don't think this is "too early" because we already have the All-Star Game as a great example of using things from early in the season as a reward.
Yes, All-Star voting.
All-Star voting last year started December 20 and ended January 21.
Is that too early to figure out who the best players are for the season? To start counting votes before the halfway mark, based on what guys did in the first 6 to 8 weeks of the season? And votes on December 21 count just as much as votes on January 16th, don't they?
All-star voting is different. Players already established themselves as an all-star caliber player by mid-season and besides it's an individual award that doesn't count towards anything.
You can't award a team a playoff spot before the mid-season break, playoff spots should be awarded at the end of the season as the playoff and championship-contending teams have already separated themselves from the pack. Teams 7-10 all are within range of each other, either a few games above .500 or sitting right at .500, so it makes sense for them to compete at season's end.
You don't want a team that finished between 20-33 wins making the playoffs over a team that finished around 40-45 wins. That messes up everything and no sports league has ever done that. The NBA would be a fool to implement that.
The only way this idea of an automatic playoff spot makes since is if the league expands the playoff seeding from 16 teams to 20 but that's a nother conversation and even then it just further goes against the play-in tournament which means you'd might as well eliminate that.
Would you rather have the in-season tournament or the play-in tournament?
The play-in makes sense as the incentive is basically an end of season do or die situation to get one of the final two spots but the in-season tournament and it's incentives and proposed ideas just are too complicated to implement.