My guess is that you can get dozens of deprecation warnings, you should first focus on DeprecationWarning, and ignore PendingDeprecationWarning. But Antoine’s explanation makes sense. Maybe PendingDeprecationWarning don’t make sense anymore.
In practice, it’s common that a PendingDeprecationWarning introduced in version N is not converted to a DeprecationWarning in version N+1, just because everybody forgot about it. It’s also common that scheduled feature removals don’t happen
I’m open to change the -X dev option if it was your question. FYI you can already ignore PendingDeprecationWarning even when using -X dev.
-X dev has a lower priority than PYTHONWARNINGS and -W options by default, so you can override warning filters set by -X dev.
-X dev show PendingDeprecationWarning, whereas -X dev -W ignore::PendingDeprecationWarning ignores PendingDeprecationWarning.
Another example, PYTHONMALLOC has a higher priority than -X dev. So “PYTHONMALLOC=debug python3 -X dev” uses the default memory allocator, it doesn’t force to use debug memory allocators.