@cxberger, it gets even better. They've literally handwaved the issue:
"""
We discussed this regression in today's rust-lang/libs-api team meeting, and agree there's nothing to change on Rust's end. Those repos that have an old version of time in a lockfile will need to update that.
"""
https://github.com/rust-lang/rust/issues/127343#issuecomment-2218261296
So yeah, they knew prior to the release, and they've done it anyway.
@mgorny yeah, i saw that. i did a little more poking about and i guess this is the Stated Policy, Actually (https://rust-lang.github.io/rfcs/1105-api-evolution.html#minor-change-implementing-any-non-fundamental-trait) but agree it's frustrating :(