Confirming Bank Cannot Refuse A Claim By A Beneficiary

[simsun2516]

I want to quote from CDCS study material which created a confusion in my mind
QUOTE "Presentation of documents by the beneficiary − in UCP 600,
sub-article 7(a), the issuing bank’s undertaking applies if the
documents are presented to the nominated bank or to the issuing
bank. If the confirming bank is the nominated bank and the
beneficiary makes a complying presentation to the confirming
bank, the issuing bank cannot refuse a claim made by the
beneficiary in respect of that presentation if it is not honoured or
negotiated by the confirming bank, on the basis that presentation
had not been made to the issuing bank within the validity of the
credit."UNQUOTE
QUOTE"Further to the above, the following should be noted:
Unless the documentary credit indicates otherwise, the confirming
bank cannot refuse a claim by a beneficiary in respect of a
presentation made in compliance with the documentary credit and
not paid by the nominated bank, on the basis that presentation has not been made to the confirming bank within the validity of the documentary credit."UNQUOTE

Please explain