Mudabir sorry for the delayed answer.I just received the following answer from engineering department:
I’m not aware of any spec provision that results in this change. At the same time, I’m not aware of any spec provision that guarantees a duration less than 20 us.
According to this, there is no issue with the xHCI controller. There is no requirement in the xHCI spec that required controller to send this less than 20 us.
Allan.