for reason(s) beyond my knowledge, the content provided here does not match the content in the original English page. I'm not sure if this will change in the future, but for now, I'm translating based on the content from the original page.
Also, I'll paste the content I see here:
Except for some legacy groups, A group's storage is not given automatically upon creation. Instead to grant a Group storage you must share that storage from another non-group account.
And the content from the original page:
Except for some legacy groups, a group's storage is not given automatically upon creation. To grant storage to a group, the group creator or a member with Shareable storage must share storage with the group.