It looks like SpaceX says 5 years for passive deorbit in their FCC filing. If a satellite were pulverized, I would expect the small pieces to have higher A/m and deorbit even faster.

https://www.reddit.com/r/SpaceXLounge/comments/ekyibk/commen...

It's not a good look to criticize an org for being careless when you haven't even put bare minimum effort into seeing if they were careful.