Ok, this thing is indeed just a simple variable resistor that drops the voltage and therefore not suitable for an AC motor but after a bit of research I find that not all light dimmers are created equal and the rheostat type is considered the "old way" of building them but they are still very common, the one I just cracked open
was purchased less than 6 months ago. Seems the "new way" (power saver type) to build them is about the same principle as a motor controller and it would seem that as long as the rating is not exceeded it might work but it would have to be this newer power saver type.
This is the ones I was familiar with (a simple variable resistor or rheostat) and I mistakenly assumed that most were still made this way. I have no idea how common these are compared to the other type but I am sure they are still very common because as I said I bought a couple of them not long ago.