APE 18: What does it really mean for other runtime dependencies?

This sentence in APE 18:

*Versions of other runtime dependencies released 24 months prior to a non-bugfix release.*

I guess I cannot understand what "prior to a non-bugfix release" mean. I need examples.

As of writing this, `astropy` has this in its `setup.cfg` and 24 months ago was Nov 2020:

* `pyerfa>=2.0` -- This was released in May 2021. 24 months ago includes 1.7.1.1. So, why not 1.7?
* `PyYAML>=3.13` -- It is 6.0 now. 3.13 was released in July 2018. Why didn't we bump to 5.4 (released Jan 2021)?
* `packaging>=19.0` -- It is 21.3 now. 19.0 was released in Jan 2019. Why didn't we bump to 20.5 (released Nov 2020)?

Do the optional dependencies count as "runtime" dependencies or we only bump as needed?

xref https://github.com/astropy/astropy-tools/pull/177 and https://github.com/astropy/astropy/issues/13930

Read APE 18 and the linked astropy-tools pull request 177 and astropy issue 13930 first. Compare the stated 24-month rule with the pyerfa, PyYAML, and packaging examples, then clarify what “prior to a non-bugfix release” means and whether optional dependencies count as runtime dependencies.

Written by the indexing model from the issue text.