I don’t know, a regular person reads the statement about the person sent not being greater than the sender and it reads like a common sense observation that the sender is obviously greater than the person being sent. A Trinitarian reads it and thinks, “well technically, they could be equal, if we ignore context, and common sense, so yeah let’s go with that, they’re equal.”
Plus there is the fact that Jesus flat out says, “the Father is greater than I”. There is that too.