I don't know the process they use, but it would not be unreasonable to harden such thin blown glass with a "pickling" process. This would make it much harder (to resist scratching), tougher (more difficult to crack), and more safe (breaking into many pieces rather than a few jagged ones). The process replaces smaller (typically Na) with larger (typically K) ions putting the outside of the glass in compression.

Notably, cell phone glass (eg Gorilla) is similarly hardened and can go down to 0.7-0.4mm while maintaining these properties.

Shockingly strong! I've always wanted to see the glass blowing process at their factory in Tokyo, but they've been closed for tours while upgrading for at least ~2 years before covid (when I was frequently in Japan).

My understanding is that they use some type of cold annealing process that strengthens the thin glass.

I've not managed to break one in 4 years of dinner party use.