This is to improve the javadoc of scan#setMvccReadPoint. Ya it was added for internal thing so that the scan is able to use the mvcc point.
But the java doc is not explicit and does not tell the importance of using it and I think internally the code just ignores it. I can confirm that once where exactly it happens but javadoc should highlight it I believe.
At least we should mention that user setting any value will be ignored.