Try doing it with coderpad IDE with no autcommplete. On top of that, for Java, make sure you declare everything as static, because top level class has static on it.

A reasonable middle ground is that I demonstrate I know all the concepts in the interview and I can send a fully compilable version after the interview.

>>I'm 43 myself, it's not something I do for fun but I can certainly code up a DFS/BFS implementation or something similar in 40 minutes.

Do you think you can do or have you done this? There is a difference between the two.