I for one don't believe that the late Queen personally wrote the Buckingham Palace Statements any more than I believe that the King writes his own speeches. Of course they sign them off and tweak them, that's how it works.
However if focussing on the "recollections may vary" statement, attention should be given to the whole sentence: While some recollections may vary, they are taken very seriously and will be addressed by the family privately.
It means that different people have different views of what was said and it is being investigated. Very diplomatic indeed, but far from calling anyone a liar, wouldn't you say?