Those were stabilized in https://github.com/rust-lang/rust/pull/161712, which just barely missed the cutoff date for 1.100 and is on the 1.101 release train.

(As for why they weren't stabilized at the same time: because it's not worth adding more baggage to a major, difficult stabilization process; as that would just be more surface area that has to be reviewed and another source of potential issues or delays. Instead, the stabilization process for infallible_unwrap was started immediately after `!` was stabilized. That process includes a 2-week final comment period for community feedback which is why they landed in different releases.)

The six week release cadence means that stuff like this is not a huge deal, and it's honestly kind of insane how consistent it's been over what's now 100 minor releases over 11 years!