I consider any claims this fundamentally unreliable because there's too much propaganda value in lying, especially during the opening phases of a war. I also don't consider Khamenei that significant; he's an important theocratic figure obviously but doesn't have the same kind of weight or charisma that his predecessor had.
Disagree about the first part. Israeli intel agencies have very deep roots in Iran, and could very quickly be humiliated if Khamenei popped up with a jeering rebuttal to their claim.
Israel also doesn't tend to report on major kills that didn't happen. It's one thing that they are fairly reliable on. If they say someone is dead, they likely are.
