Practice exam question about Azure DevOps PaaS or SaaS

I just took the Practice exam and came across this question:
What kind of service architecture is Azure DevOps. With options On-premis, SaaS, Serverless, PaaS or IaaS.

I chose SaaS, which was incorrect with the following explanation:

INCORRECT ( SaaS ) – Azure DevOps allows you to control a bit of its configuration and how it functions, so you don’t use it as an end user. Because of this, and the level of responsibility you take for its function, it is not considered SaaS. What is SaaS? Software as a Service | Microsoft Azure (this is a link to https://azure.microsoft.com/en-gb/overview/what-is-saas/)

Where as PaaS was stated as correct with the following explanation:
CORRECT ( PaaS ) – Azure DevOps is a Platform as a Service (PaaS) solution, where you manage the platform and the services on it, but not the infrastructure. Azure DevOps Services | Microsoft Azure (this is a link to https://azure.microsoft.com/en-au/services/devops/)

And this is what I don’t understand SaaS should encompass everything that PaaS is, thus it would mean that one of the criteria in SaaS would not be met. If I look at the definition of SaaS (in the link) I don’t see what criteria is not met, so from that definition Azure DevOps is a SaaS. If we then take a look at the explanation it states that because you control a bit of its configuration and how it functions it is not used an end user. Which sounds kind of strange because I have no clue who then is the end user of Azure DevOps? If we follow that logic I would also not be the end user of Outlook of Office 365  because I can change the configuration and how the software functions by adding inbox rules or writing a custom function in Excel.

I can make an argument that it can be used in a PaaS solution. Where Azure DevOps is used as a Development tool, then it becomes part of a PaaS solution but that still does not change the service architecture of Azure DevOps.

So what am I missing here or is correct answer wrong?