I doubt Mrs Merkel had phoned round the other 25 member states and checked their view on this. She does regularly clear things with France. I do not think she was formally speaking for the EU, which has entrusted this to their Negotiator in chief. I do think once again she revealed how the modern EU works. Germany is the leader, and Germany feels she can say these things, safe in the knowledge the others will accept them. There was no sudden outpouring of disagreement or protest at her reported words, nor any official denial.
As someone who thought simply renegotiating the backstop was insufficient given the nature of the rest of the Withdrawal Agreement, it serves to underline just how committed to this draft Treaty the EU is that they will not even countenance changes to one of its worst features. It does not augur well for future talks or imply with some more give and take there might be an agreement. Mrs Merkel has condemned a modest UK proposal to deal with one of the bad features of the Agreement without offering anything back and without implying she is willing to compromise on anything else.
Yesterday the government confirmed it will be leaving the EU on October 31st, deal or no deal. It looks as if the EU wants a no deal result or think they can find a way to stop Brexit altogether. Such is the damage to the UK’s negotiating position the Parliamentary opposition to Brexit has now done.