Hello Mirof and anybody else,
See the message below that I had already seen on the EXPO 2020 website re accommodation in this hotel. As can be seen this explains the lack of availability. One might be suspicious that the Special Reduced Rates may not be either reduced or special:-

NH Eindhoven Conference Centre Koningshof has a special offer for you during the World Model Expo.

Advantages over other deals:
•No advanced payment required.
•Special reduced rates
•Free of charge cancellation of your room reservation is possible until 7 days hours prior to arrival,

Please be informed that the special rates at the NH Eindhoven Conference Centre Koningshof will also apply to other NH hotels in the vicinity (except NH Collections in Eindhoven centre) for your stay during the World Expo. The required promotional code will also be published on this website on July 1, 2019

Room reservations for the World Model Expo 2020 weekend will be possible 12 months prior to the event, meaning that you cannot make your room reservation before 7th July 2019

My main concern is that it looks a bit out of town, estimated to be 9 KM to the centre of Eindhoven. The website has a hyperlink button that lists other accommodation. I've checked out yet the alternatives.