Why is priority video given to the thread here?

According to the documentation

public static final int THREAD_PRIORITY_VIDEO

Standard priority of video threads. Applications can not normally change to this priority. Use with setThreadPriority(int) and setThreadPriority(int, int), not with the normal Thread class.

Constant Value: -10 (0xfffffff6)

So I run the following code onCreate() of an Activity:

Log.d(TAG, "In UI Thread");
Log.d(TAG, "Thread.currentThread().getId() = " + Thread.currentThread().getId() + ": Thread.currentThread().getPriority() = " + Thread.currentThread().getPriority());
Log.d(TAG, "Process.myTid()  = " + Process.myTid()  + ": Process.getThreadPriority(Process.myTid()) = " + Process.getThreadPriority(Process.myTid()));

Thread thread = new Thread(() -> {
    Log.d(TAG, " ==========In new thread===============");
    Log.d(TAG, "Thread.currentThread().getId() = " +  Thread.currentThread().getId() + ": Thread.currentThread().getPriority() = " + Thread.currentThread().getPriority());
Log.d(TAG, "Process.myTid()  = " + Process.myTid()  + ": Process.getThreadPriority(Process.myTid()) = " + Process.getThreadPriority(Process.myTid()));
}
thread.start();

The output is:

In UI Thread    
Thread.currentThread().getId() = 1: Thread.currentThread().getPriority() = 5    
Process.myTid()  = 6424: Process.getThreadPriority(Process.myTid()) = -10    
 ==========In new thread===============  
Thread.currentThread().getId() = 9113: Thread.currentThread().getPriority()   = 5    
Process.myTid()  = 6440: Process.getThreadPriority(Process.myTid()) = 0  

My question is:
Why in the UI thread the priority is -10 which is THREAD_PRIORITY_VIDEO?