Ok, the reason for high octane in 2 smokers is the oil lowers the octane of today's gas. You may get away with it, but it is a risk to run less. You have to remember that the only oil protection every thing inside the motor comes from the oil mixed into the fuel, there is not oil pressure at the bearings on the crank and the RPM's that 2 strokes run are much higher, so detonation wipes them out MUCH faster than a 4 stroke motor.
Pounded out crank bearings could be detonation. Or you may have had a load of "wet" fuel that soaked the bearings and rusted them. Alcohol in any form tries to soak up water when it can. The amount that is supposed to be in today's fuel is not supposed to cause problems with water or corrosion in the fuel system. I am still sceptical of these claims. I got to see what happens to a 2 stroke engine when you fail to purge alcohol fuel out after a days running the hill. The carbs were gunked up, and anything steel inside the crank case has rust on it.
What brand of oil did they sell you? Just like engine oil, it's not all the same stuff. In my Stihl equipment is factory oil, or klotz R50. I mix at 3 0z of oil per gallon of premium fuel and have tuned the carb to that mix and R50. I do not switch fuel grades or oil, this is asking for a melt down, and I check the plug color often.