So I tried to apply for a clockwise trip of Rae Lakes Loop via the National Park Service. With good reason they limit the number of people per day and stagger them. I could not get the dates I need.

Another packer said you can approach from the US Forest District side (Onion Valley Trailhead) via Kearsarge Pass which connects to the Rae Lakes Loop. And since the US forest district isnt as strict and booked it was easier.

Etiquette question. Is that cheating? If I start on a national forest side and hook up with Rae Lakes Loop I can just camp in any of the scheduled campsites along the way of the trail? Im confused at why National Park Service can be be bypassed that way.

Thanks all.

It's not cheating. There many routes in the Sierra, and many destinations. There are only a few (Donahue Pass SOBO from Yosemite, Whitney zone) where a permit from one authority isn't good in another jurisdiction.

For example, I tried getting a permit a few weeks ago in the Sierra NF. I could get a permit easily, but explicitly NOT for any itinerary that included Yosemite. That is unusual, and the ranger apologized for it. You may find that Inyo gives you some specifics about Rae Lakes when you get your permit.

I often look at lesser known trailheads or routes to get where I want to go, and that includes permits for different entry points.

You can always call and ask. That's what those phone numbers are for.