Yeah, I kept waiting to eventually hear that this was caused by some other random issue, and not them expecting deterministic behavior for floating point ops, but they actually confirmed it a few days ago in their blog: https://www.halowaypoint.com/news/closer-look-halo-infinite-...

The relevant section is:

"The first cause is rooted in the fact that the simulation needs to be deterministic. This means that when the client performs an action, the result of that action is the same when the server performs it."