I'm a bit rusty in my theory, so I'll gladly retract this if someone can tell me otherwise, but...

If I recall correctly, an Altered chord is simply a generic name for chords that go beyond "Extended" chords - they have their own specific name which is often forgotten because of the theory involved behind them. Alt isn't necessarily the name of the chord, just an indication that it is non-standard (root, 3rd, 5th), or extended (root, 3rd, 5th, 9th, for example)

I believe Dominant and Diminished chords are classed as Altered chords, where as Dsus4 is classed as an extended chord. That would explain why you can have the same chord "name", even though the theoretical structure is different.

There's more theory behind all this which I can go into if you'd like, but I'm hoping that should be succifient to answer your question

I'm 99% sure that's right - would anyone care to prove or disprove the remaining percent?

Hope that's of some use...