Most engineers I've worked with have been trained, implicitly or explicitly, to only speak when they have a complete thought. You figure out the answer first, then you present it. Uncertainty is something to resolve privately before you expose it to the group.
This is backwards for collaborative problem-solving. The whole point of getting smart people in a room together is the interaction. If everyone arrives with pre-formed answers, you don't get thinking together, you get negotiation between positions. That's much worse.
The board helps break this pattern, but it has to be introduced carefully. If you walk into a room and draw a perfect diagram and then ask for feedback, you've recreated the same dynamic digitally. The diagram needs to be visibly rough. The questions need to be genuinely open.
What I do now: when I'm facilitating a technical discussion, I come to the board with one or two things I'm confident about and everything else left as questions. I draw the confident things, I write the questions as literal questions with question marks, and then I stop talking. The open questions pull people in. It's hard to sit in a room and look at an unanswered question without wanting to answer it.
Over time I've seen this change how my team talks about problems in general, not just in board sessions. They've gotten more comfortable sharing half-formed ideas. They ask more questions in public. The culture shifted from present-your-conclusion to think-together, and I think the physical practice of drawing on a board while uncertainty is visible was part of how that happened.
You can't fake rough. That's the thing about the whiteboard that I don't think has a digital equivalent.