Retirement tax questions

THIS SEEMS TO BE A GRAY AREA.  THE UNPAID RMD FOR A DECEASED IRA OWNER BECOMES THE LIABILITY OF THE BENEFICIARY WHO HAS OPENED AN INHERITED IRA.  THAT POINT IS CLEAR. BUT SOME SOURCES SAY THAT EVEN IF THE IINHERITED IRA IS CASHED OUT, TAX ON THE UNPAID RMD IS STILL REQUIRED TO BE PAID IN ADDITION TO THE TAX ON THE TOTAL LIQUIDATION. SOUNDS LIKE DOUBLE TAXATION. I HAVE SEARCHED THROUGH IRS GUIDELINE AND BOOKLETS TO NO AVAIL. AND THE IRS SEARCH ENGINE IS ABYSMAL  GOOGLE AI GIVES CONFLICTING ANSWERS DEPENDING ON HOW THE QUESTION IS POSED. NO ONE CAN REFERENCE BACK TO A IRS RULE OR OPINION ON THIS.