It angers me to hear that.
My rules for filling a tank:
Must be in hydro
If it's an aluminum tank that isn't a 3AL, it must be in VIP that guarantees it has been Eddy'ed
If it has a thread insert, it must be stamped for high pressure service, or made of steel.
With that being said, we currently have in our shops a pile of relics that customers have "bought at garage sales" or "were getting out of the hobby"...In it, is an 1800 psi, "Property of US Gov't" stamped 1944, WWII aviation O2 bottle, with a steel bushing in it. It carries a hydro stamp every 5 years, the neck is almost completely full. The last hydro date was in the 90s.
If it was in current hydro, I would fill it.
Why?
Because I'm not a jerk who makes up rules to make a buck. I know the engineering : If the tank isn't neglected, passed hydro, and is in current visual, it'll be fine.
The only part that sucks about the bad alloy tanks : Eddy current testing takes time, time is money, which results in a higher yearly maintenance bill for you.