My Greek is not that hot but I do know Οἰκουμενικόν as in Ecumenical Council means "Worldwide" or "General" Council, it doesn't mean the same as getting together with other Christians as this guy implies. This is the type of ignorant tosh that gives ignorant tosh pedlars a bad name.
I've heard it countless times before.
It rather puts you off of buying a second-hand dodgy Cathedral from him, though possibly it makes him a good candidate to buy one.
p.s. What is a "worship space"?