Because SaaS isn't cloud computing. SaaS is essentially a fully available software application that you don't run on your own machines.

There's similarities, but key differences that you can easily look up to better understand. Hence part of why most aren't huge fans of including O365 to claim Azure's bigger than AWS.

If the claim is that Azure is generating more revenue than AWS, then yes I would say that is misleading.

If the claim is that Microsoft's cloud revenue is bigger than Amazon's, I would assume that includes Office365. Office365 isn't just Word and Excel on the desktop, it's Outlook, Dynamics CRM, Sharepoint, Teams, etc.

Do you think Amazon subtracts their own massive utilization of AWS out from their numbers? Not likely.

How is buying your own product GAAP? None of the cloud providers can claim their usage of their own products as revenue, it is a cost.

Do you think it’s a major fraction?

I doubt it, but that’s just speculation without anything to back it up.

So any concrete data would be interesting.

Because most of the revenue is from businesses buying it to install Office on their computers and not using any of the online services.

Whether or not a company is taking full advantage of Outlook, Flow, Sharepoint Online, etc doesn't really matter in terms of revenue. If a company is paying for cloud products, that counts towards Microsoft's cloud revenue.

Even if the bulk of the Office365 ecals they're selling are for the lowest tier offering that still includes Outlook and Onedrive which a lot of organizations use fairly heavily.