Why are some command-line arguments deprecated?

I’m using Hugo v0.40.3 and when I run hugo --help these command-line arguments are listed as deprecated:

  --canonifyURLs 
  --pluralizeListTitles 
  --preserveTaxonomyNames 
  --uglyURLs

What does this mean? Does it mean I should not set these on the command line or that I should not set them in config.toml or both? If it means these variables should not be used at all, please remove them from the All Configuration Settings section of https://gohugo.io/getting-started/configuration/ and put them in a Deprecated Configuration Settings section with an explanation about why each is deprecated.

Thanks!

Here is the relevant section of hugo --help:

Flags:
  -b, --baseURL string             hostname (and path) to the root, e.g. http://spf13.com/
  -D, --buildDrafts                include content marked as draft
  -E, --buildExpired               include expired content
  -F, --buildFuture                include content with publishdate in the future
      --cacheDir string            filesystem path to cache directory. Defaults: $TMPDIR/hugo_cache/
      --canonifyURLs               (deprecated) if true, all relative URLs will be canonicalized using baseURL
      --cleanDestinationDir        remove files from destination not found in static directories
      --config string              config file (default is path/config.yaml|json|toml)
  -c, --contentDir string          filesystem path to content directory
      --debug                      debug output
  -d, --destination string         filesystem path to write files to
      --disableKinds stringSlice   disable different kind of pages (home, RSS etc.)
      --enableGitInfo              add Git revision, date and author info to the pages
      --forceSyncStatic            copy all files when static is changed.
      --gc                         enable to run some cleanup tasks (remove unused cache files) after the build
  -h, --help                       help for hugo
      --i18n-warnings              print missing translations
      --ignoreCache                ignores the cache directory
  -l, --layoutDir string           filesystem path to layout directory
      --log                        enable Logging
      --logFile string             log File path (if set, logging enabled automatically)
      --noChmod                    don't sync permission mode of files
      --noTimes                    don't sync modification time of files
      --pluralizeListTitles        (deprecated) pluralize titles in lists using inflect (default true)
      --preserveTaxonomyNames      (deprecated) preserve taxonomy names as written ("Gérard Depardieu" vs "gerard-depardieu")
      --quiet                      build in quiet mode
      --renderToMemory             render to memory (only useful for benchmark testing)
  -s, --source string              filesystem path to read files relative from
      --stepAnalysis               display memory and timing of different steps of the program
      --templateMetrics            display metrics about template executions
      --templateMetricsHints       calculate some improvement hints when combined with --templateMetrics
  -t, --theme string               theme to use (located in /themes/THEMENAME/)
      --themesDir string           filesystem path to themes directory
      --uglyURLs                   (deprecated) if true, use /filename.html instead of /filename/
  -v, --verbose                    verbose output
      --verboseLog                 verbose logging
  -w, --watch                      watch filesystem for changes and recreate as needed