Technical note - the verse in John is about past.
Then the world will know that you sent me and have loved them even as you have loved me
John 17:23
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
KJV
This is the aorist active indicative; which is normally translated as our simple past tense; however, there is a special use of the aorist, which continuous action outside of time. I believe that usage is operative here!
Matt 3:17
17 And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
KJV
Here is an example of the aorist being used the same way.
If, indeed the aorist in Jn 17:23 does signify continuous action outside of time, then the English present perfect is indeed the best translation.