Why is the (major) pentatonic scale called a scale? You can only build two different triads out of one, and it just sounds like a normal diatonic major scale with two notes left out (so it can is compatible with three different major diatonics). It doesnt help that hardly anyone composes in this 'scale' but rather uses it for melody over something that is in a diatonic scale. Modes arent considered scales, so why is this?
Your thinking appears to be confined to the notion that all scales must act like diatonic scales. Firstly, what are commonly thought of as "modes" are actually chordal labels for the tonic of each diatonic scale relative to a given ionian scale. So technically, modes are scales. Secondly, the pentatonic mode is simply a progression of notes scaled to five notes per period. Chords, in the diatonic sense, are related to each other in a way which produces cadence. In the pentatonic scale, "chords" are simply the relationship between one note and another, without necessarily needing to interact with contextual "chords"; since this concept is so similar to the diatonic concept of chords, it's easy to confuse them.
Why do some theoreticians claim that two enharmonic notes are somehow different aside from their names? Look, I'm pressing C# on the piano. Now I'm pressing Db on the piano. They're the same key producing the same pitch: the only thing that determines the correct name for the note is context.
You have to be careful. This is true on the piano with the equal temperament we're used to nowadays. They can, in fact, be not quite the same pitch with other temperaments; your professors just might not be doing a good job of explaining this.
Yes, context is what determines names for notes. That's why we name them to begin with, to denote the range of possibilities that they have for relationships with other notes around them.
Specifically, it has to do with what's called "note spelling." In standard usage a scale should contain one tone for each letter name, so in A major (for instance), "A, B, C#, D..." is correct because "A, B, Db, D..." wouldn't make sense. Meanwhile, Ab major goes "Ab, Bb, C, Db..." for the same reason. Context is exactly the point.