This is from the 88 service manual, should be the same as the 89.

 

I was surprised to see that the factory manuals shows the axle being inserted from the left. It's better, where possible, to insert the axle from the right. In the event of a wheel bearing seizure the axle will tighten rather than loosen the axle nut.

 

In the event of a rear wheel bearing seizure you want that axel nut to turn loose, specially at high speeds. Otherwise you might just drag that rear tire to a stop if under control, most likely a wreck. And for that axel to turn there has to be years of corrosion built up between the bearing and the axel.
Worst case scenario the bearing failure causes the axel to turn loosening the nut allowing the tire to spin again and maybe just maybe regain control of the rear end.
Should you worry of this happening, yes if you do not follow your bikes manufacturer maintenance squedules. Case in point my 1988 cane had so much corrosion between the rear bearing and the axel that I had to pound the axel out with a drift pin and small sledge hammer to get it out so I could correct a backwards installation of the chain adjusters. Bench grinder wire brushing all the pitting and spraying on some dry lubricant tuck care of the problem.
Also the axel is not going to slide out due to it being seize in the first place, and the swing arm has to get hit by a lateral blow to get it to open enough for the right side to come/slide out once the nut falls off.
Its easier to torque the nut up too 69 foot pounds while applying the break as per design.

PS My location is prone to cause lots of corrosion due to the tropics nature, rain is normal drought is not. Also the island is only 100x35 miles so salt water gets blown in with every storm that comes by.