I can't count the number of times I've wanted to to get into flow and couldn't because the dev experience doesn't get enough attention.
... or because my story is vaguely defined I have to stop a few times to get clarification.
... or because I need a decision from several people.
... or because I need help from someone who only checks email twice a day to avoid distraction.
When discussing breaking flow, HN tends to focus almost exclusively on meetings and communication (eg email or slack). These things are a big problem for maintaining flow. But I find they aren't the only thing, and many other flow breakers exist that are solved by meetings or communication.