Possibly, Greece did not realise how much the world’s press would seize on the relatively brief remarks  made by culture Minister Nikos Xydakis regarding plans not to take legal action.
Whilst many newspapers have been busy printing stories  some of which are mainly conjecture, based on a few lines from a speech, the Greek government were already backtracking, emphasising that they were not writing off the idea of legal action – but that it was just one of many avenues open to them that they were exploring.
So – we read from this, that Greece is not committed to opening legal proceedings in the immediate future, but the idea is still on the table for potential use at a later point in time.
One must go back though to the original statement a few days before  – that Greece must “use it or loose it”. They might not have all the time in the world to wait before taking legal action.
I am disappointed to see that very few news sources outside Greece have chose to cover this retraction of the original story – continuing to go to town on the original news, despite the fact that it is no longer correct.
Greek Reporter 
Greek Culture Ministry: Legal Action is One of Many Options Available for Parthenon Marbles’ Repatriation
May 15, 2015
Seeking legal action is only one of the options available to Greece on the issue of the return of the Parthenon Marbles, Alternate Culture Minister Nikos Xydakis said on Thursday, following his statement on Wednesday that the government will not sue the British Museum on the issue.
Asked about Greece ’s strategy on the issue, the minister said: “Legal opinions are extremely useful and reinforce Greece ’s arguments for the return of the Parthenon Marbles, but the Greek government has never stated it is committed to initiating court proceedings in the near future.”
He added that “legal action is just one of the many paths opening before us” and that the struggle through diplomatic and political means has yielded “impressive results” already.
Xydakis also noted that public opinion in Britain is in favor of the return of the Marbles.