Hmm, but if this is the case... the shining ones are axis? IF we stick to the orgirinal setups from ancient SIU stuff axis were beings with godlike nonsensical powers. They had a hierarchy which phanta towered over (other than SIU of course). The stronger axis were in charge of stories out of which the tower was just one among many. And an important one at that. In this old setup defeating phanta was a conceptual impossibility as phanta as an axis was basically omnipotent. It's not an issue of numbers or strength, phanta is basically in charge. Only a stronger axis could theoretically oppose him.
So I am thinking there are two scenarios:
1.- SIU scrapped the old axis concept. In this case we just gotta wait and see how things play out and apparently urek would be some manner of axis which is unrelated to the godlike nonsense originally framed.
2.- The concept has not changed and both phanta and urek are operating under the old rules. If this is the case the perhaps shining ones are just part of some other story which phanta meddled directly with for some reason. In this case of course a trillion ultra instinct ureks wouldn't be able to tickle phanta.
The terms might have been changed to King with the concept behind it staying true. I don’t see much point in SIU scrapping it since they still touch upon the subject.
google translate still but Headon apparently tried denying Urek’s entry into the tower as he isn’t supposed to be changing the story inside (a set story by another axis, probably the one Arlene prayed to) but was inserted in due to Phantanium’s appearance inside, as he is the now confirmed strongest god, he likely alter the original story inside the tower to some extent.
Plus, other named axis has been titled/called the King of Conquerors etc. so the framework is still holding up.
As for Urek, he might not have awakened his true powers yet or he is still withholding/strengthening it. He did seem like a teenage entering the tower at the time so he hasn’t matured his powers yet.
Regardless of whether Urek can truly do the impossible and defeat the monstrosity that has killed six of his predecessors and turned them into gems, this is already enormous hype for Urek separating him from the likes of the other irregulars (13 Great Warriors) with a very clear distinction.