So Intel swiftly came in this morning and removed the 28 core CPUs from both ASUS and GIGABYTE's systems. It sounded like they gave the companies 20 minutes to hand over the parts
— Ian Cutress (@IanCutress) June 6, 2018
No official details about the reason behind this move, but it appears Intel was taken by surprise by AMD's 32-core processor. HardOCP speculates one of the reasons may be the huge power draw of the 28-core Intel chip. The cooling system used for the 28-core demo was definitely pretty extreme, considering AMD used nothing more than a beefy HSF for its 32-core chip. The Intel demonstration required a 1600W Corsair AX1600i PSU and the Hailea HC-1000B chiller.
AnandTech also writes that Intel's demonstration was heavily cherry picked as just one of the prototypes on display was actually capable of hitting a 5GHz frequency.