This is a simplistic take. Of course trust is a pre-requisite to a healthy team, and people should feel comfortable speaking out, there's no debate about that. However, transparency is not a silver bullet. I've seen plenty of teams that trust each other but don't get very much done. And if what you are doing is large and involves more than a two-pizza team or challenging tradeoffs then effective communication becomes much harder. If everyone just speaks their unfiltered thoughts without thinking about how those words will be perceived there is a high likelihood of confusion and churn. There is also the matter of expertise, and the fact that many important truths may not be grokked by all stakeholders, so just blurting them out may lead to furrowed brows and unproductive lines of questioning—or worse—a bad decision fueled by misunderstanding.
This makes sense, and it helps a lot when conversation is focused and concise (while also allowing for a small amount of redundancy: people may acknowledge and display their receipt of previous messages by repeating them in their own words).
When you mentioned communication becoming harder: were you referring to audio/video discussions (in-person or otherwise) and/or also text-based messaging?
That isn't a claim. The claim is that a team with full transparency is more effective (in terms of work done) than one with a limited transparency.
What's interesting is there's talk about one-on-ones like they are an acknowledged best practice, but nothing about established payscales (or open salaries).
> Of course trust is a pre-requisite to a healthy team
it is hard to rust someone on the team with technical tasks when that person is not technically capable for a developer.