Why? The problem with Grizzly isn't that it is rough, the problem is that the layout is miserably dull. The turns are taken slowly, there's minimal to no air time, there's just a general lack of forces. Timberliners wouldn't suddenly make the ride ten times better, it would make it smoother, sure. But even as a smooth ride, Grizzly would still be a sub-par coaster for the terrible layout.
Agreed. Grizzly's problem isn't roughness as much as it is dullness. Hell, you'd need to put a rocket-powered Ferrari on the track to make that ride interesting.
However, there are far worse wooden coasters than Grizzly (for example, Anaconda at Walygator in France).