Originally Posted by HTupolev

That won't work. Shimano changed their 10-speed road compatibility in 2015 when they launched Tiagra 4700, and that includes GRX400.

The cassettes use the same spacing as the old 10-speed standard. But, the rear derailleurs are now compatible with the new 11-speed road stuff. To make this combination work, the new 10-speed shifters pull a different amount of cable per shift than the old 10-speed shifters.