Apologies for the slow response, was trying to find a source, but haven’t found one.
My comment was based on personal experience of going through secondary inspection with border agents in various countries. All of the FVEY countries share a frightening amount of information with each other’s border agents. I’m not specifically claiming they have medical records, but literally anything that is in a government database (I’m not being hyperbolic there, just prefer not to be specific as to what I’ve been shown on their screen that I felt they had no right to know) is accessible to them if the agent wants and knows how.