I'm trying to understand why would I have less security if I disable a replay attack protection in OpenVPN config. It's not really explained in the man page, only
Don't use this option unless you are prepared to make a trade-off of greater efficiency in exchange for less security..
As far as I understand, an IP packets can be duplicated by design and every application using an IP should be ready to deal with it. And it's not a theoretical possibility, WiFi networks can produce duplicate packets. TCP stack is ready to handle duplicate packets, so for any TCP connection there's no problem with duplicate packets.
So the only problem I could see is that some buggy application might use UDP protocol and it's not ready to correctly handle duplicate packets, so attacker might produce those duplicate packets and trigger unusual behaviour. Is that correct? Is there any real facts of such vulnerabilities?