Yeah, as I said, don't expect anything to be consistent.
I've flown through a few airports, both class B and class C, mostly in and out of California but a few other places as well, and mostly in the last year or two. The only time I've ever unlocked the gun case while inside the airport was one time when the airline (not TSA) wanted a written statement that the gun was unloaded to be placed in the box. I think that's the sheet you are talking about. I filled it out, unlocked the case, cracked it open enough to toss the sheet in (never opened the case enough for anyone else to see in), locked everything back up, and that was that. That sheet isn't required by some airlines and even on a given airline it isn't always asked for. The law says you must certify orally or in writing to the airline that the gun is unloaded. Telling the person at the check-in counter fulfills that obligation unless the person wants a written certification. Airline's choice.
TSA people don't need to see the firearm to verify it's unloaded. Nobody needs to see the gun. You just need to certify that it's unloaded. The TSA will verify your certification/that the gun is unloaded because if they catch you lying that's a criminal charge for you and they like that (makes their numbers look better) but they can check with an X-ray machine as well as with a visual inspection.
I even went so far as to offer the TSA guys the keys one of the first times (when I was still nervous about the whole thing) and the screener's response was "I don't want that... just wait here while we x-ray the bag and if we need anything we'll call you." A few minutes later the guy waved me on my way.
On the destination side, so far I've always just gone to the carrousel and eventualy my gun case (or bag with gun case inside) has popped out.
Does that mean that my next experience, or your experience, will be anything like that? No... I'm only reporting what I've encountered. I actualy expected the CA side to be a lot worse and now that I think about it the time I was required to fill out that little sheet was one time when flying out of CA but in any case it hasn't been much of anything out of the ordinary.
I should point out that I've been flying with fairly run-of-the-mill handguns (that were legal in both locations... no full-cap mags in CA or anything silly) and I have been careful to do things like seperate ammo and guns clearly. Different bags usually. One flight did have a fairly empty pelican case... I have a bunch of pelican cases but one of my favorite is the 1510... if I'm not carrying a gun I can use it as a carry on bag and if I buy a gun as I'm traveling (C&R license) I can slap some padlocks on the outside and check it as a pistol case on the way back. It also has wheels and works fairly well as a roll-around case. Thumbs up on the 1510.