You're forgetting that some individuals are perfect and never make a mistake and, unfortunately, judge all others on that basis. Back in the real world, some of us are more forgiving.
I contacted supporter services and they replied and, with their agreement, below is the text of their response. This should clarify the situation. Mistakes happen, and, generally, don't think anyone can really complain about the service from the ticket team.
Good morning Drew,
An error was...
Just spoke to the ticket line and they said they are not on sale yet as the actual date has to be confirmed. The information about the 18th was on the basis that we didn't beat Millwall apparently!!!!