If you are fully virtual there’s going to be no water cooler talk

Physically, yes, unless you're attempting to recreate a water cooler in VR or something. However, I would argue that offtopic slack and teams channels and direct messages offer similar benefits. Dedicating time at the beginning of meetings to just chat, or otherwise encouraging off-topic chatting can also be a decent stand-in. This can all be enhanced by being a little bit more openly personal at work - having worker directories or homepages where people submit pieces of information about themselves or customize it to their liking can also convey the same or similar information that's shared in water cooler talk environments.

When I said they fail to account for this, it's that they aren't comparing to mediums which convey the same information in different ways. They're comparing a rich, diverse communication environment to a deprived one. These considerations are important when you're trying to make the evaluation of whether the medium is at fault or whether you've just poorly controlled additional factors.

I don’t think you can. Take for example board games as an in-person activity. The virtual replacement would be video games. A video game can do everything a board game can (with some exceptions) - but it can do so much more. So, purely from a game design perspective, video games would be much better. The main thing that video games don’t have, while board games do, is the in-person interaction. Yet, there’s plenty of people who play board games, but not video games. Clearly the in-person part is important.

This isn't a well-controlled comparison. You're comparing two vastly different things. Comparing board gaming in person to VR board gaming might get you closer to understanding what is important or higher quality about an in-person interaction versus a virtual one, but even then there's still many aspects which are tough to control for. Generally speaking most science I've read on the subject has to do with the quality of communication present. Comparing text to audio to video mediums we've found out many important differences between modalities of communication. With only text, it's difficult to fully understand what people are trying to communicate - adding an audio medium allows for a more complex message to be conveyed, which is once again improved with the addition of body language and further complexity which comes via video. The difference in complexity of message between video and in-person mediums primarily has to do with the quality of the signal and the tools permitted. The difference in how we perceive the two has a lot more to do with personal preference and complexity of the message than anything else. There are important considerations to be made here, but I have yet to see any studies which show any meaningful difference in message between the two mediums, unless we add additional complexity such as messages which involve other senses such as ones which incorporate smell or touch.