I think there you defend against "extend" but Fedi-developers being vigilant and holding the line on the API's etc they are willing to ingest and output.
A bit like Podcasting, where you stay standards-compliant and ignore any dependentcies the Apple or Spotify-only add-ons to the RSS or non-compatible formats.
That has actually worked well so far and kept the standard so "plays anywhere you get podcasts" claim works.