There might be no benefit to you but the people who would be the direct targets of every hate group like LibsOfTikTok currently active on Threads probably feel a bit differently.
This is in no way a knee-jerk reaction to a hypothetical alarm. Meta have directly contributed to a genocide and allow hate groups to grow unchecked on Threads. It blows my mind that the fediverse - itself built as a series of alternatives to shitty companies doing shitty things - thinks the harm Meta will do is hypothetical and unproven.
The benefits to not federating are many, but the best one, in my opinion, is not exposing current fediverse users who will be targeted to those who will target them.