DD didn't say the 300bar tanks had inserts. He said some one tried to fit a 232bar DIN to a 300bar tank.
Ummm, did you read what he wrote that I quoted?
"All (pro) valves even on Ali tanks around here are the 300bar type."
A Pro valve has an insert, by definition. That's what makes it a Pro valve. Right?
So, he's saying they have valves with inserts that are 300 bar.