Sengun is 23. He averaged basically 20/9/6 with 3.2 turnovers per game playing for one of the worst offensive coaches ever.
Brown has never averaged more than the 5.1 apg he had this year and he did that on 3.6 tpg. Brown scored more, but also shot more. They have similar points per shot.
Sengun is 6 years younger and doesn't play the same position as Boston's best player. Brown was better this year, but I'm not so sure he will be next year or any year in the future.
Also because Sengun makes about 20 million less, it wouldn't be a 1 for 1 trade though the tax implications make it hard to work out a trade. This one works before the season flips.
Sengun, Finney-Smith, Sheppard
for
Brown, Garza, Scheierman
Not sure Houston does that, but it at least makes sense for both teams.