When I first was listening to this, on Firefox, the E6 and D#6 sounded like the same note, with Chrome they sounded different notes.
It doesn't. You're just listening from your PC speakers
I'm guessing you're using Firefox. This is a bug in Firefox. Nothing we can do about it. Try using Chrome, edge, or opera
I think Calico was able to fix the bug locally but I dont know what he did to fi it