> I would consider the amount of shift is not going to be reliable enough to enable an efficient start, especially if a load
> is involved.! It is far from the ideal of 90°

My simulation was just a guess at the values and shows that phase shift can exist without a start capacitor.,
"Better" circuit values could result in closer to your ideal of 90°.

Also consider that my washing machine has started for about 50 years without a start capacitor...

 

I just realized that my circuit leaves the start winding energized when the motor switch is in the Off position. That's not very safe. It would be better to use a Double pole, double throw switch to disconnect the start winding also when the motor switch is in the off position.

 

Like so: