By Revold 15 Comments
Here's a legitimate theory I've been thinking of for a while. The "Ultra Instinct" Goku who fought against Jiren is not a good reflection of his true strength. Right before he was about to fight Jiren, Goku was able to shake the infinite world of void, a "Jiren level" feat, and tore through dimensions with sheer force, also similar to Jiren's power which is said to transcends time itself. This is similar to Goku Black's feat of tearing apart spacetime itself, who is stated by the director Kido to be the strongest non-GoD character, and obviously those above GoD doesn't count. So if that statement still holds true in ToP, Jiren and UI Goku would be stronger than most, if not all GoDs, making them universe level (not unlikely looking at their feats).
However, if you look at the Kefla fight, UI Goku is stated to be inferior to LSS2 Kefla, by pure physical stats like attack potency, durability and speed, while his reaction and fighting skills still holds superior. LSS Kefla is around SSB level (both slightly stronger than Super Vegito), and LSS2 Kefla would be around twice of that. LSS Kefla it not spirit bomb level (check out @dottiestmoon's thread).
If fatigued UI Goku is weaker than LSS2 Kefla, a fresh UI Goku wouldn't be suddenly Jiren level, would he? While he does have the UI to match him, he still must have some amount of power to match someone like Jiren. The explanation is obvious and straightforward: Goku did absorb the Spirit Bomb/Genki Dama, which gives him a temporary boost to give Jiren a harder time than SSBKK.
But if Spirit Bomb-amped UI Goku can give Jiren trouble, why couldn't SSBKK-pushed Spirit Bomb? Because 1, Goku has the UI technique on top of his raw power, which is actually the more important aspect of the transformation and 2, Goku probably pushed the Spirit Bomb with just Kaio-Ken x10. Kaio-Ken requires huge Ki control, which probably increases with the multiplier. This is why you see when Goku uses Kaio-Ken x20 against Jiren, he uses it in short bursts and depowers quickly to gain back his speed and agility. Note that he did the same against Fused Zamasu, which might imply that he already learned x20 (not unlikely when he went back to present several times to prepare himself).
So conclusion, SSBKKx20 might be superior in raw strength, but loses in agility, reaction, and even duration he can use it for. Remember, power is not all about potency (attack potency charts etc), it is also about abilities like instinct and fighting skills. UI might still be stronger than SSBKKx10, but I'll leave that to your headcanons.
If you are still not convinced, this isn't the first time for an over-representation of a transformation at awakening. Suppressed Beerus, after thrashing SS3 Goku, he said that "I'd have to fuse with Vegeta, even then I don't think I could win". Beerus actually used more power against SS God Goku than that, so is SS God stronger than Super Vegito? No, in fact SS God Goku is only slightly stronger than base Vegito, scaling from the Kefla fight. This might be because he was given the Ki of the five saiyans, Vegeta and Gohan included so its not a laughable amount. Which also could explain how he can match Beerus' supposed "universe level" punches. After that, he had to consume his own stamina. Remember, we don't know how credible Goku's statement is, so he might be over/underestimating, but this is just a supporting argument, so don't worry about it.