The problem is that with Chelsea being one of the five 'early adopters' of safe standing is that it meant they had to provide a number of safe standing seats to away supporters. 12,000 safe standing spaces have been. Normally for Premiership games only one tier of The Shed end is available for away fans. Cup rules requiring 15% of the ticket allocation has meant the entire 6,000 allocation being safe standing.
Below is the guidance - no mention of the conflict between those wanting to sit.
I suggest post match that this issue is raised with the authorities as surely the option of a seat should be available - Cup game or not.