Reveal & Planning
Indeed, Daneel was entering the Kingdom of Arafell… as a rat.
According to Drakos, the formation could scan both lifeforms and consciousnesses at any level. Yet, there was a certain loophole that wouldn't have existed if they were living in the age of the Empire of Angaria.
Apparently, the original formation, when deployed, also had a secondary part where a fine-tuned search would be carried out of each and every organism entering the formation which would have resulted in this plan failing.
Yet, because the second part was the one which required a lot of materials which were not available right now, the Queen had chosen to subvert that by building the smaller, second one around her Palace while the larger one was around her borders.
Essentially, this large formation, which was easy to implement, was only designed to scan large beings.