Nowhere on Haringey's CPZ website pages do they say which type of fixtures require a permit and which do not.
Well, the website does link to the address you found but it goes on to say:
To ensure you do not miss any fixtures, Arsenal has also set up an automated calendar download service (external link) (https://www.arsenal.com/calendar) to notify supporters and local residents when match dates are set. Alternatively, please ring the Arsenal switchboard on 020 7619 5003.
Please note:
• Some events take place at Arsenal's stadium that are not listed in their football fixtures calendar - for example, concerts, rugby matches etc.
• Please refer to the parking signs within the Finsbury Park CPZs that show the dates and times of upcoming events
Details of events in Finsbury Park are listed in our what's on calendar. (https://www.haringey.gov.uk/whatson)
Did you simply stop reading at the first link? Or did you check the other two?
In the meantime I'll find out if they updated the signs.
@wignula you've paid the PCN so that's the end of the matter. If you pay a PCN it would be helpful if you told us, so that we don't waste time investigating it.