Whatever you call it, it is the canonical hours of the Catholic Church.
As far as I know, the canonical hours, along with Mass and Divine Liturgy, are all considered “liturgy”, in other words the public prayer of the Catholic Church. In other words, if I go to Mass, I have participated in “liturgy”. If I go to Divine Liturgy at the Byzantine Catholic Church, I have participated in “liturgy”. If I pray Vespers or other Hours, I have participated in “liturgy”, even if I pray them by myself in my living room. I would presume ECs consider the hours “liturgy” in the same way.
However, if I participate in any other type of prayer service, such as one where a priest gives a talk, we all say some individual prayers, and then we all pray a Rosary together, I have NOT participated in “liturgy”. It’s not considered public prayer of the Church, even if there’s 1000 of us and we’re in a public cathedral or park.