I think you're referring to the line "if he hit me for real, even once, it might have ended ugly.", which is on page 42 (give or take, I might have counted incorrectly) of chapter 58.
But like I said in the CRT, Garou repeatedly deflects and reflects Metal Bat's Low 7-B swings, any of which could likely one shot him. This is why I proposed Garou's tier should be "High 7-C+, higher with WSRSF", but since you raise a good point with the X1.5 downscaling (making Garou roughly 454 kilotons) I think his tier should be "High 7-C, higher with WSRSF", since his defense and offense (to the extent that he can reflect more powerful attacks) are much higher with this technique. Garou's fight with TTM showed us this was the case, but Metal Bat shows us that Garou can handle people that are entire tiers above him so long as WSRSF can deflect/reflect their attacks.