The 'defiance' they're talking about are the projects that Canonical has developed, often in secret, which are or were essentially alternatives/competitors to the components of the Linux free desktop stack which have been developed in the open, often at Red Hat and developed on Fedora.
The cases that come to mind are:
- Unity vs. GNOME 3
- Upstart vs. Systemd
- Mir vs. Wayland
- Snap vs. Flatpak
The Canonical entries all appear as sort of NIH latecomers, whereas their competitors have generally been developed in an upstream-first, 'release early' kind of way. In each case, the tech opposite Canonical's has been shipped on Fedora, before eventually becoming the default in Ubuntu anyway. (Snap has yet to go.)