Hi and thanks for reaching out. My name is William. I'm a Windows technical expert. I'll be happy to help you out today.
This is because Spotify is included as part of the UWP app "bloatware" of Windows. In order to install the desktop version, you need to remove the local UWP binaries, that way the desktop installer wont push you to the UWP app version. To do this:
Uninstall the app version if you have not done so already by right-clicking the App in the Start menu and selecting Uninstall. You can also do it from Start > Settings > Apps.
Next, open File Explorer > navigate to C:\Program Files > go to the View tab in file explorer > check the option for Hidden files > in C:\Program Files scroll down until you see the WindowsApps folder > right-click > select Properties > Security > Advanced > next to Owner select Change > under "Enter the object name..." type in Administrators > OK.
When ownership change is complete > go inside the folder and delete the SpotifyAB.SpotifyMusic_1.138.558.0_x86__zpdnekdrzrea0 folder.
Grab the full offline installer from https://download.scdn.co/SpotifyFullSetup.exe. When the install completes, you can confirm the desktop version is installed by opening appwiz.cpl and locating the Spotify.