It’s perfectly adequate for stability. People have suspended printers in midair with elastic cables, or printed upside down, and prints have come out fine. The printer frame is providing most of the rigidity in this case. Don’t get me wrong, people that place their printers on spring like things tend to get lower quality prints so there is a limit there.

The downside about the IKEA particleboard over hollow cardboard core is more about sound and resonance imo. It can act as a speaker for printer vibrations and amplify that sound in the same room or to the floor below it.

A popular “mod” is to place a concrete paver block on top of some isolation pad, typically made of rubber or sorbothane to increase the functional mass of the printer and lower the resonant frequencies created during printing.

I personally have two of those enclosures stacked, with a printer in each one.