Fair enough - although I suspect I won’t be the only one asking (even if I’m the first 
). Rsync for example has a --size-only flag which skips files that have the same size (ignoring time).
I read here https://kopia.discourse.group/t/recognizing-duplicate-inodes/396/2
Kopia generally avoids rehashing files if the attributes (name, modification time and size) match the last snapshot - it will simply assume that the file has not changed (this behavior can be overridden).
I’m interested in exactly how to override this behavior. I couldn’t find it in the docs, but I will take a look at the source code.