Sadly, when communicating with people, important things have to be repeated over and over. Maybe less so with highly trained and experienced people on something that their training and experience make the statement plausible, but if the thing is at all surprising or diverges from common experience, I've found a need to bang it out via multiple communication channels.
I learned this lesson as an engineering manager / tech lead. I got frustrated at how often I found myself having the exact same conversation with different people... until I relapsed that communicating the same core information to different people was a big chunk of the job!