From the same link (the warnings are even color coded)
In order to keep our systems up to date, we sometimes need to carry out essential maintenance. So that we don't cause you too much disruption, we do this in the early hours of the morning from 02:00 to 02:40.
When we have essential maintenance planned outside of these times, we will update the information below with the specific times and services affected. We are sorry for any disruption that this may cause for you.
Now a regular person would suggest that any downtime outside of 2:00-2:40 am is abnormal and not regularly scheduled. I guess we will see tomorrow if they warn about Oct downtime.
Also worth noting that the website has no scheduled downtime.