as far as I know, every product advertisement is an exaggeration. every brand boast about it's products more than its capable of.
u wear a deo and get chicks faster than James Bond in ads.
likewise there are many.
even sennheiser does it.
I bought HD 518, and the label it had was ''deep rich bass sound'',that was misleading to a newbie. I wasn't cause I knew years before buying it that open headphones are low on bass and so wasn't expecting it.
I also know quality vs quantity thing.. tight controlled bass and all,but that too wasn't there.
their bass is neither tight nor deep and rich nor is the amount high enough to be labeled as muddy . infact it doesn't deserve the label.
I don't know about beats much other than name of dre and a couple times I visited it's website.
but regarding false advertising ,every brand does it.
But then again if you compare them to something more similar in comparison, the HD518 and HD558 really has much better bass than something like a AD700.