If you format an empty note as task, the cursor is placed in front of the dash – so when you start typing you will still end up with a note with a trailing dash.
If you format a task as note when the cursor is at the end of the line, it will jump to the next line. I assume, the cursor tries to preserve the position in line and as two characters ("– ") are actually being removed from the start. You can watch this behaviour, if you place the cursor somewhere in the middle of the line and switch between note and task. May be this can be easily fixed.