All threads that I have read in the past interpret the permit as access to the "wilderness area", not to the portal. In fact, no permit is needed to hike up to Lone Pine Lake (or further), so cannot see how that could be enforced.
On a separate note, to achieve your goal, you will have to be making very good time (particularly with a full pack). Less than 6 hours from the portal to the top, in the dark, comes with some risk. Several people have died on this trail, by going off trail without realizing it (usually coming down). The area above Mirror Lake comes to mind as one spot where others have become lost. You did not mention your dates. Will you have a full moon? That would improve you chances of a problem free assent.
Thanks for the input everyone and I appreciate the comments, John, regarding safety when hiking in the dark, especially in that area above Mirror Lake. The good news is that I've been on the Whitney Main trail almost every summer for the last 10 years, so I am aware of those risks and issues. Having said that, this thread has helped me think through the scenario a bit. Regardless of my experience, I'm leaning toward adding an extra day and starting at a more normal time. I CAN do that 16 or so miles from WP to the summit and over to Guitar Lake/Crabtree in one long day with a full pack, but why take that extra punishment if I can simply add a day and break it up? Sometimes my goal oriented mind gets ahead of my 57 year old body.
My entry date is actually July 18th and it appears I may have an extra permit. If anyone is interested and available to hike that day, let me know. If it ends up unused as I now expect, you are welcome to join me. No need to commit to the full hike to Onion Valley.
Otherwise, I will cancel the extra slot and make it available for others to find on Recreation.gov.