Indeed the night and day differences people describe when upgrading already competent gear are absolutely ridiculous. Would I call it fraud? Maybe not, but overstated fir sure and I get your point.
Adding couple of competent subs to a 2.0 system would still be considered a huge objective improvement though, providing one or in some cases two octaves of audible information.
That is as close as it gets to "night and day" differences if you already have something more than a clock radio for your music listening.