Those trench raids were much more common early on in the conflict before the full drone apocalypse set in. I have to imagine it's at least 100-1000x more common that a drone drops a grenade on a trench than it is for the two sides to be close enough to reach out and touch each other.

And if we're talking about China I think it's safe to assume that their drone force would dwarf anything we've seen in Russia/Ukraine.