Claims of priority

I was looking at this week's Phys Rev Letters, and I saw this paper being highlighted as an editor's suggestion.  Now, I don't know anything about this work, but I was struck by the title, which says explicitly that this measurement is the first of its kind.  This is repeated a few paragraphs into the paper at the end of their introduction.  I thought that claims of "first"s were very strongly discouraged by the editors, as mentioned here, let alone being included in the title, regardless of how well founded the statement.  Was this an oversight, or am I missing something?