Hi there

The reason for phase button is to eliminate some audiophiles suspicions about correct phase of the disc. And another issue is that most of pirate records (Bulgarian for example) seems to be recorded in inverse phase (this could be a reason for a poor audio quality)... this could be a reason for good or bad records…

1. plug phase (IEC) – some brand preffer to inverse phase in order to work better with their cable or with same brand components.
2. microphone phase – in order to obtain the accurate reproduction of sound probably the best sound engineers know this litlle secret of correct microphone phase checking.
3. speaker phase – here is no doubt that factory specifications for + and – must be respected…

So this phase standard seems to be a troian horse against audiophile. If u are a dealer u can switch phase of IEC in order to make some electronic device sound better or worse depend of your personal sale interest.
If u are a company who produce a variety of products from media centers to speakers, u have a better control of this … u can make a beter compatibility between electronix.
If u make just speakers u have also two options : u can ignore the phenomen or not. 

In other way... I still preffer easy ways to make things works.

Best regards