IRCC, when he was hooked up to the machines, it wasn't stated his strength was growing exponentially. It's been a while, but I'm pretty sure that scene suggested that his strength was growing at a slow pace. It would take him hours of amping to break out of the force block or something.
I still don't understand why people think Thor needed to have been amped in any notable way for the Thanos fight. During that fight, it was acknowledged that Thor would give Thanos a run for his money any normal day. Which is exactly what happens whenever Starlin has the two meet.
Albeit, Surfer said that Thor was more powerful than all of them put together at this point during the recap at the beginning of the previous issue. Of course, there are a few problems there. The main points being that Surfer never encountered Thor since he got his ass handed to him and learned only in the previous scene that Thor had got his hands on the Power Gem. The second point is that there was no notable difference in Thor's power levels from the previous fights.
Edit: Was Thor catatonic during the force block imprisonment? Thanos believed that to be the case but IRCC, Thor was able to trick Moondragon. I'm not 100% clear on that scene going only from memory but if Thor was conscious and actively tapping into the Power Gem, then this has some implications.