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 made this morning and an on sale for Tottenham did show for a brief time. However this shouldn’t have shown as no official communication has gone out from the club.
Due to our progression in the FA Cup there are multiple dates still in the offering of when this game could be played. Therefore you will receive a refund today and further information with regards to the correct date and time for on sale will be communicated in due course.
Please accept my apologies for any inconvenience caused.
Just to clarify, I didn't actually buy a ticket so won't be getting a refund!
The correct response, as any sensible person would agree.
(But not those who bought tickets for themselves or others who weren't in the top tier for loyalty points)