The article itself is deliberately vague.
It says:
"A heated ‘debate’ on social media is not how any important policy should be made.
Rather, decisions on guidelines should be informed by robust evidence and developed in consultation with players and athletes with direct experience."
misleadingly implying that World Rugby haven't studied this issue thoroughly, and that Stonewall didn't try to inflame the debate on twitter AFTER the findings of the investigation were made public.
It's not clear what Stonewall's desired endgame is. Even if it were possible to specify a particular safe standard for safe competition, some people who identify as trans under Stonewall's criteria would be excluded. Stonewall might want all sports to be mixed sex, but that isn't a realistic goal.
Stonewall really seem more interested in publicising Stonewall than improving the lives and protecting rights of trans people.