as one of the instance mod/admin’s I’d say that evidence would help expedite the report process but it’s totally optional
depending on what the thing being reported is sometimes evidence isn’t needed
for anything that’s blatantly negative/unpleasant, evidence isn’t typically needed when reporting a post/comment
for anything else that someone might find subtly “off”, 2 pieces of evidence could help us figure out what’s wrong
as a systems analyst having as much information to determine what happened and how things got to this way can help others and myself determine what the best way forward could be
for example some users might just need a warning/clarification based on my own interactions