In short, as long nobody overfills and heats the CO2 storage bottle, a 1000psi rated setup will be perfectly safe- pressure technical-, even without 1000psi pressure relief device.

As the rules changed over the years, to the detriment of pneumatic machines (Oh woo betide the machines build to 2003 rules for series 7, consumables.... please of gas-options. No more nitrogen, helium or simular. No, only CO2 and 1000psi Compressed air, thank you) and the advantage for hydraulics (from 3000 psi to 10000psi... woha, funny bit, only people with deep pockets or extensive hydraulic knowledge can benefit.).

Also, the failures on pneumatic machines I have seen, and experienced myself weren't pressure related, but speed and mass.
The decoupled Gravity setup (from it's ancestor Hammerhead II) removed that point of failure for most builders.

In short, is the Burkert 5404 valve, if used properly in a FP setup unsafe or not?