Team's Response

Reasons for rejecting:

"As a user, you want to understand the basic features of the application": This is already addressed by the entire User Guide.
"or where to even start with all the tabs": How to get started is already addressed by the Quick Start section of our User Guide (see screenshot 1 below), which explicitly lists down the steps for the user to get started. What each tab does is already concisely described under each tab in the User Guide (see screenshots 2 to 6 below).
There is no requirement whatsoever that there must be a section titled "tutorial" in the User Guide, so this report seems more like a suggestion rather than a bug, and suggestions should be rejected (see screenshot 7 below).
The User Guide itself serves as a tutorial for the user. The developer team has deliberately arranged the content of the User Guide so that it flows from top to bottom. That means that if you follow the User Guide starting from the top, the content is arranged just like a tutorial for you, because it brings you step by step through every tab. For example, you will explore all commands for the Dashboard tab first, then explore all commands for the Contacts tab, etc.
Even if you jump to a specific tab in the User Guide, you can immediately understand what each tab does by reading the description of the tab (see screenshots 2 to 6 below)

Reasons for changing severity from Medium to Low:

Even if the tester insists that this is a bug rather than a suggestion, the severity should be Low because it is unlikely to affect the normal usage of the User Guide. As mentioned, the User Guide is already sufficient for the user to familiarize themselves with the app, since it already provides a Quick Start section, a comprehensive explanation of what each tab does, and coverage of the features under each tab, which are all arranged in a coherent manner from top to bottom.

Screenshot 1: