It is confusing, but Form 5884 is NOT used for the Covid-related PAYROLL tax ERTC credit.  The 5884 instructions say:  "Qualified wages do not include the following wages:  Any wages used to figure a coronavirus-related employee retention credit on an employment tax return, such as Form 941, Employer's QUARTERLY Federal Tax Return."

5884 is used for other disaster-related credits and is an income tax credit.  The Covid ERTC is a payroll tax, not an income tax, credit.  So booking the payroll tax credit as a receivable makes sense.  And I believe, but am not sure, that the amount of that payroll tax credit must reduce deductible wages on the Form 1120S.  But in any event, it is not an income tax credit and will not appear as a credit on any K-1.  Instead, as you say, you will have a receivable for the future receipt of your payroll tax refund arising from claiming the credit on an amended payroll tax return for the fourth quarter of 2020.