Yaw values in the sample code (visualize)

[trivikramak]

A small change in the actual object's (say board) orientation (Yaw) is changing both the Yaw and Roll values given by the library by a lot. But, the visualizer is showing the orientation changes correctly.

When I changed just the Yaw of the board by approximately 10 degrees, the values returned by the library changed from 258.55 -76.74 -78.69 to 107.18 -83.89 82.95.

Don't the Yaw, Pitch, Roll values returned by the library represent the rotations about axes ?
Why can't we use the Yaw, Pitch, Roll values directly to rotate the 3D object (Instead of applying matrix transformations) ?