This was a major conference of Islamic leaders from across the Islamic world and this fatwa is authoritative. It is no small thing.
Additional details can be found here, and at RAIR
“The secret of all victory lies in the organization of the non-obvious.” -Marcus Aurelius
History shows that all lands dominated by muslims were stolen from others, particularly from Christians.
So, it’s not surprising that this muslim is either knowingly lying or he’s delusional. Either way, the muslims should return their stolen lands to their rightful owners.