It contradicts basically everything since Trunks and Goku sparred.
Ch. 15, pg. 37.2.-4
Context: As Trunks recovers from sparring
Goku: “You surprised me!!! I can’t believe you managed to get this far on your own!!”
Trunks: “Ah, well… Even still, it was nothing against Black…”
Goku: “I thought it would be a piece of cake, but I guess we’re in trouble…”
Not only did this imply someone that could stomp Trunks was "trouble" for Goku and Vegeta, it now looks like a lie.
Ch. 20, pg. 19.4
Context: after Goku Black transforms into Super Saiyan Rose
Goku: “Vegeta. Maybe we should actually start working together now?”
Vegeta: “Don’t mess with me. You go take care of the other one! This isn’t gonna get anywhere if he keeps reviving and powering up.”
Lie.
Ch. 20, pg. 30.1
Context: after Vegeta’s been defeated
Trunks: “Goku! We must retreat! If this keeps going, we’re all gonna die!”
Nonsense.
Ch. 23, pg. 29.4
Context: after Goku is knocked into a building
Goku: “I’ve got no power left…”
Masochist.
Ch. 22, pg. 35.1-2
Context: Goku has just turned Super Saiyan God
Trunks: “What?! You’re also gonna use Super Saiyan God?”
Goku: “I lost quite a lot of energy using the Mafuba. Going Blue right now won’t work for long. Well, for you, I guess this is more than enough.”
Note: He’s talking to Zamasu at the end there.
We knew this was a lie from the moment Goku went to fight Merged Zamasu.
Ch. 23, pg. 25.5
Context: after Goku is hit by a Klangite cube
Zamasu: “Those are Klangite -- the hardest known material in the universe. Can you not even hold your own against mere objects?”
Ch. 23, pg. 26.2
Subject: Goku
Trunks: “At this rate, he’s most likely going to lose…”
Ch. 23, pg. 26.3
Subject: Goku
Gowasu: “If he could only make his stand for one more hour… However, as far as I can see, that might be beyond all hope…”