What is lying? What is a lie?
This isn't like an Abrahamic religion where one offers prayers up to a deity. Many religions don't have prayer, but something that roughly is kind of similar as a means to an end.
People keep saying prayer, but it's kind of like calling a meditative chant a prayer.
Constitutionally, if this opening ceremony is to occur it cannot be restricted to prayer. It's only called opening prayer because of traditional norms,
And, ideally, it's best left to the "none at all," because it's a silly fracus to have it to begin with once we start allowing them all.
But it has shown us where many stand on freedom of religion. Clearly many don't actually believe in it or support, save for when it favors their own personal beliefs.