Premultiplied alpha exists to solve one problem: multiplying by the alpha channel is common to almost all of the Porter-Duff compositing operations, and computers used to be slow, so premul came about as a way of speeding up drawing operations. Instead of multiplying each time, you simply multiplied the alpha channels in advance.

Unfortunately, this causes a ton of problems when you're doing anything with transparent images outside the realm of Porter-Duff, since the process is not fully reversible. In addition, it has tainted the way that developers think about alpha channels, so that they erroneously act like there is only One True Clear Color, which is how we ended up with issues like the one described in TFA in the first place.

Premul is not the solution. Premul is the original problem.