True. These are those that are "surprising" and not usually tracked. If I get an issue that some dependency releases a fix that I care about, then I bump the minimum.
Yes. Unfortunately, this means that the MSRV creeps up as crates have varying views of what it means for stability. -Z minimal-versions keeps that stable at least.
It's easy enough to force a bump by adding a direct dependency to the crate to your own Cargo.toml file. I typically comment it with a link to the issue(s) related to getting a dependency bumped.