The gravity device in the laboratory was originally designed to test the performance of Mecha under changing gravity conditions. Fatty used it to train control and hand speed; probably, he was the only one in the Federation who did this. Some people might have thought of it, but they didn't have the conditions to train anytime and anywhere.
During the battle with [Vajra] while rescuing Russell, Fatty had understood the true meaning of Mechanical Combat. So, after his hand speed hit a bottleneck, apart from using various sneaky moves, his real training focused heavily on combining basic commands with fighting skills.
In Fatty's view, being sneaky is in his nature, it doesn't need training at all. He just didn't know how Milan would react upon seeing [Logic] with that thing installed — whether she'd be so shocked she'd pass out, or she'd simply blow him away with random gunfire.
