My understanding is that the canon nature of the spherical Daedalus Class ship is vague to say the least?
Sisko had a model of one in his office, and it was the spherical configuration ship. It is true there is no specific line of dialog that states that the model on the desk is actually a Daedalus class ship.
Bear in mind that Sisko served at the Utopia Planetia shipyards on Mars helping to develop new ships. This heavily implies that a ship of the configuration existed somewhere in the Trek timeline, since him having the model implies he has an appreciation of ships/ship construction from his time there.
The Daedalus class is canon but has yet to have its appearance confirmed as the design we see in Sisko's office as canon.