Coincidentally, since I asked this question a long time ago, Mundorf finally wrote back today. I asked them specifically what they meant when they said the the caps would "break".
They said:
"What I meant:
The Mlytic Series are polarized electrolytic capacitors.
They need to be operated with the correct polarization in DC use cases.
Also they work with modulated AC components over DC – the harmful part is the change of the polarization when the Voltage crosses the zero point.
If you have a low load, it could be that they work with AC but it is not guaranteed how long the capacitor will work.
That is the reason why unipolar film capacitors are used in crossover networks – they can handle AC in high voltages or currents."
They said:
"What I meant:
The Mlytic Series are polarized electrolytic capacitors.
They need to be operated with the correct polarization in DC use cases.
Also they work with modulated AC components over DC – the harmful part is the change of the polarization when the Voltage crosses the zero point.
If you have a low load, it could be that they work with AC but it is not guaranteed how long the capacitor will work.
That is the reason why unipolar film capacitors are used in crossover networks – they can handle AC in high voltages or currents."
