Exactly. Frieza most likely knows the only person able to defeat Jiren is Goku so Frieza is going to help him.Whis has been teaching Goku and Vegeta to achieve this Ultra Instinct since the beginning of their training too.
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I haven't been watching Super enough to even know that until a few days ago but the thing mentioned in the episode is, they don't understand his "heat"... kinda odd way of putting it.
I noticed a few times that Goku looked completely relaxed, and maybe he was able to tap into it before Vegeta since that's Goku's whole gimmick while Vegeta is always uptight.