I'm not sure what scale would affect this that Google hasn't already hit? I've already had GSuite for my high school, my college, and my work. What additional scale would open up massive security holes? This seems like it's very much just horizontally scaling the same product.

Not to mention that GSuite already has 6M different customers/tenants. They're already at a comparable scale, and that doesn't mention that the free versions have the same application security model, with zero incidents (knock on wood). "but scale" feels like it's ignoring the already existing track record and scale and just making excuses for Microsoft.