<span>Past perfect tense is used in this case. This is due to the fact that the events are not in normal chronological order. This tense is used to differentiate when the events happened and put them back into proper order.</span>
The present perfect tense describes actions that began in the past and continue into the present or that have just been completed at the moment of speaking or writing. The present perfect often suggests that a past action still has an effect upon something happening in the present.
Your keyword is "nonessential" which means you don't need it. So the statement is true a nonessential element is not necessary for the meaning or the structure of the sentence.
