SDK initializing even though "Initialize XR on Startup" is not checked

[Marie-DAS]

using Vive Wave Unity SDK 5.3.2

Situation:
Unexpected behaviour regarding the initialization of the Vive Wave Unity SDK.
NullRef from the UnityInputSystemUIInputModule in non XR scene when "Initialize XR on Startup" in the XR Plug-in Management is not ticked.

"NullReferenceException while resolving binding 'Submit:*/{Submit}' in action map 'DefaultInputActions (UnityEngine.InputSystem.InputActionAsset):UI'
UnityEngine.InputSystem.UI.InputSystemUIInputModule:OnEnable () (at Library/PackageCache/com.unity.inputsystem@1.3.0/InputSystem/Plugins/UI/InputSystemUIInputModule.cs:1376)"

This NullRef results in not being able to interact with any UI Elements in the non XR scene.

Expected behaviour:
No XR (HMD, Controller, Tracker, etc) initialization when "Initialize XR on Startup" in XR Plug-in Management is not ticked.

Additional Information:
When in "ViveWaveWristTracker.cs" line 92 "Initialize()" is directly returned, the NullRef described before is not thrown.
The non XR scene with the NullRef error does not contain any XR components (no XR Rig, just a normal camera).
When in the XR scene (with XR Rig) with "Initialize XR on Startup" not checked is started the NullRef does not get thrown. But the Initialization still happens even though it shouldn't.