This needs some clarification.  Actually the IRS form 706 is filed by the estate of the decedent and the tax is paid by the estate.  If you mean by this the heirs receive less because of the tax, you are correct.   Only in rare cases do the heirs see the details of the 706 filing and amount of tax  paid including the generation skipping tax.   Maybe there would be more widespread opposition to this tax if the heirs filed a form and paid the tax directly based on what they receive.  More transparency.