We may be debating how many angels can dance on the head of a pin here, but fwiw I *think* that the TSA guidelines have changed. I am pretty sure that at one point the TSA website said that you MUST use non-TSA locks and that you were not supposed to give the code or keys to anyone and that you had to be present when the case was opened. (I'm pretty sure because I had an argument with TSA on this point - more below.)
Now the guidelines not only permit TSA locks, they now (that I could see in the link above) no longer recommend against TSA locks, and they seem to give us a heads-up that TSA may want to open the locked case - with no reference to the owner being present. ("Only the passenger should retain the key or combination to the lock unless TSA personnel request the key to open the firearm container to ensure compliance with TSA regulations. You may use any brand or type of lock to secure your firearm case, including TSA-recognized locks.")
Anyway, I have encountered the "no secure area" issue, including back when the TSA rules were as written before (no TSA locks and no one can open the case without the owner present). It was on my way home from Charleston, SC and I initially refused to hand over my key and I cited the rule. I asked to speak to the supervisor and the woman in front of me calmly explained she was the highest ranking TSA officer at the airport. She said she was aware of the rule, but there was a conflicting rule that prevented me from going to the place where they would open the case. She said I could choose not to fly with the weapon, or let her personally inspect the case and return the key to me. I chose the latter. FWIW, Omaha, NE has the same limitation - the inspection area is in the back behind the check-in counter (at least for Delta flights). Since I fly out of Atlanta, I can say (at least as currently set up) there is no such problem - as the oversize/special baggage place TSA opens and looks at your firearm is separate and accessible by passengers.
I've raised this point in other threads and some people don't like it, but don't shoot the messenger. My point is that when you fly with a firearm (including in a bow case), be prepared for the unexpected. If you have six locking points (like on my SKB), be prepared to have six locks on it - although some TSA agents will say fewer will suffice. I've also had locks that are mysteriously missing after a flight - but the others are unopened and not cut off - so I keep extra (non-TSA) locks with me to replace those. (Someone speculated that the locks can get caught in a conveyor belt and pulled off...?)