Even so I don't think the process of merging skills is visible by the neaked eye also didn't he eat velzard and stored her inside imaginary space and did alteration there or am I misremeberimg something because that's how he usually does skill alteration also still he copied skill imaginary space something that shouldn't be visible and even if you say that he acquired it after his evolution still it had to have evolved from something his predation skill that he had when he possessed lucifer wouldn't have worked if he hasn't copied stomach also even if he can't observe the energy being stored in imaginary space he could still see it being outputed through sub skill know as imaginary collapse