Back story as explained by Elon in an interview with Lex Friedman:

The government's environmental assessment was bonkers. They were required to do things like assess the risk of a booster landing on a shark or whale in the middle of the ocean. They were also required to assess if the sound of the rocket would harm the breeding behavior of the seal population. To do this they had to chase down a seal, strap it down to a board with headphones and study if the sound of rocket engine were emotionally distressing to the animal.

If they had flame suppression its likely they would not have triggered the additional review.