[BUG] Larger time interval is observed on received UMP message timestamp.

[m-komo]

Describe the bug
With regard to #402 , I have created a simple C++ app to trace message timestamps and callback timestamps.
Basically, it seems quite stable and small enough.

However, the time interval between the first message and the second message is significantly larger than others.
It is about one milli-second if I test on diagnostic loopback endpoints.

To Reproduce

1. Run the "receive-speed-cpp.exe" and choose the "Diagnostics Loopback B" endpoint.
2. Open midi.exe and run 'midi ep send 0x40904000 0x00000000 -p 0 -i -c 10' on the "Diagnostics Loopback A" endpoint..
3. Press any key on the "receive-speed-spp.exe" to dump received messages.

The result is as follows:

Expected behavior
The same time interval as the others.

Screenshots
I got almost same result on every test.

Installer Name or Version
Windows.MIDI.Services.In-Box.Service.1.0.2-preview-9.250121-1820-x64.exe

Desktop (please complete the following information):

• OS: Windows 11 Version 24H2
• OS Build 26120.3073

Application Information

• "receive-speed-cpp.exe" (Please compile the main.cpp)