I've played it twice with a randomly assigned partner in the "Play now" section... we didn't speak at all. Both games were won. The first was an easy win (we had lots of tunnel closes in the early tiles) but the other was far more complex and we managed to win the game with only about 10 tiles remaining. It was a really great game as both of us were quite intuitive to the shapes and areas we were starting to build and focus on.
I've also played with friends (via zoom) where we've said things like: "I've got the south-facing tunnel covered" or "I've got a really bad hand, I'm only going to be splitting tunnels for a few turns"... I very occasionally say things like "great, I picked up a U"... but only if we've previously had a discussion as a group suggesting that we leave a corner of the tunnel system that would be closed off by a U-bend.
It's definitely a game that after a few goes at it you start learning the types of shapes that will help you succeed. Infinity symbols, figures of 8 etc can be created once you feel confident with the options.