I don't thinks it's odd they decided to have a campfire on the beach, but with conflicting stories, and both making sense. which one is the truth, or does it really matter?
The question would be why do we have multiple stories?
Harold gave one story to the FBI. Pat sat by sullen not commenting. What story (stories) did Harold or Pat give others privately, before the FBI and news conference fame set in? Nobody has checked that out. We know that Pat, Harold, and Crystal (at minimum) gave accounts of the finding to a number of people prior to the FBI even being called. Crystal called several radio stations in order to enhance her chances at a reward after the meeting with Himmelsbach. Did Pat also? These people needed money, not a bunch of DB Cooper games!
Then Crystal surfaces and gives her own story, not only to the FBI but to news people! That is documented. Why news people ..... there's the rub: because THEY ALL WANTED A REWARD once they realised they were not going to get the money back. Did they think they were loaning it to the FBI?

tisk tisk

One minute their kids are pulling out a wad of free $20 twenties and are headed to redeem them at a bank .. the next minute they are having to turn it all over to scowling guys in suits with guns with no promise of even a reward ... in some famous piece of Unreality called the DB Cooper Hijacking case! WTF! How unfair and crazy does it get for the hourly blue collar worker!
They wanted money! They needed money! Either the bills back OR a healthy reward. Denied both that's where the trouble began. They lobbied hard for a REWARD with anyone who would listen but no reward was forthcoming, so to a lawyer they go, and five times around the Horn they finally arrive in Paradise! Brian still lives in Paradise!
These are common people, with common concerns. No Nobel prizes or college degrees, not even a free Carnegie Make a Speech course at night school! Just working folks out on a walk on a free beach (when you can't afford a movie or the gas to go to Seattle!).
Does this bring the Ingrams more into focus? And their motives and their stories. One story for Harold. Another story for Crystal who also happens to be in the process of divorcing Harold's brother! She needs money! The Ingrams need MONEY! So ............. off to a lawyer they go ................ to get money for all! Never mind that it will take five lifetimes and 20 bankruptcies and evictions to get it !!!
Folks this aint rocket science!
Jack n Jill went up the hill to fetch a pale of water ... Jack fell down and broke his crown .... and .... you can probably forget about complicated conspiracies and back stories involving drugs and pimps and some drug dealer the Ingrams used who knew DB Cooper who also was on drugs traveling in the same circle, and some reverse-sting to send the FBI off in some improbable direction (discovery of my loot!) and yada yada yada yada ...

The Ingrams are common folks and a divided family with lots of troubles at the time who are badly in need of infusion of cash. The last thing they need is more confusion, calamity, and less money with more attention directed their way! Harold has an outstanding warrant waiting in (New Mexico?) he has not settled. Yada yada yada yada.
If this was a conspiracy it was the screwiest conspiracy since Laural and Hardy bought Goslow Maine for $2.00 dollars only to inherit outstanding liens totaling $4 million dollars!

Only in America could this happen!