Later in the article it states that any value other than 0x31, 0x32 or 0x33 acts as an "inoculation value", so that would be a 253/256 chance for each packet of at least 1151 bytes.
It depends on what the server is doing - packets that size wouldn't be unusual in a bulk data transfer (like a HTTP response) but are larger than you'd see in the typical DNS query/response.
