Is kpdtttzrd*@privaterelay.appleid a fraudulent email address?

Define 'fraudulent'?

If you mean "is an official Apple email address', then the answer is absolutely NO.

However, that doesn't necessarily mean it's fraudulent, per se.

Private Relay is a mechanism Apple offers iCloud Mail users to generate 'temporary', or 'disposable' email addresses that users can give out, without revealing their true email address/identity. People often use it for signing up for marketing or subscriptions knowing they can cancel the email address at any time and not have to worry about their actual email being leaked.

I suppose there is some potential fraudulent use here, in that someone can use it to mask their identity, but it's most often used as a safeguard, not a fraud mechanism.

I guess it comes down to how you're seeing this. If you have a service and someone has signed up using an @privaterelay address, that just means they're protecting themselves, not that they're trying to scam you.