Bug animation window atrocious performance on baked animation

The animation in this Maya scene starts at -450
I set import as no key reduction full bake then press apply

after a while the import process finishes
playback of the timeline is now 10x slower than in maya
when I double click the clip it shows

for about 20 seconds before displaying the dopesheet keys in the animation window

and each time i do something in the interface that same hold on window appears
something includes trying to resize a window
it's unusable
it appears that the animation window display is bringing unity to its knees
and selecting the animation clip in the scene asset does this

yes, that's 30 seconds repaint!
here is what i managed to capture in between editor gui repaint

So it appears that the object wide dopesheet, that topmost line of keyframes is 100% optimized and redraw N times for every key