Are you trying to sync between color and depth? If so, Jesus G from Intel support posted the following information about the D415 and D435 models' hardware sync earlier this year:
The RGB and depth cameras are on the same PCB board. The HW sync connection between RGB and depth is in place, but the FW has not enabled it yet . It is planned for development with a release about 2 months from now.
NOTE: Jesus' message was posted 2 months ago, suggesting that the availability of hardware sync will be in the near future.
The RGB and depth sensors are not on the same PCB. The RGB is a standalone camera module, there is no HW sync connection between RGB sensor and depth sensor. They cannot be synced.
I am aware of the post you quoted. I do not want this question to go into a discussion on D400 hardware limitations.
With the recent update to the Windows UWP API it is possible to get media frames grouped in time.
Whether this is solved in hardware or in software is not important for working with the API right now.
It's a generic API that can be used for Kinect, Intel RealSense and any future sensor that may come with UWP support.
BTW the same behavior I described also occurs with the D415.