I've never really had an issue with layer time disparity on this model, using Orca with the A1/P1S. With the H2D, however, there's a very noticeable line, which is consistent with the change in layer time. The layer times(and disparity) are pretty much the same as the A1 batch, but regardless of whether I print with the door closed or open, single pc or full plate, the line is there on the H2D. My A1 is having some other problems right now so I can't do a test with Bambu Studio on the A1, but I'm wondering if someone that uses both Orca and Studio has noticed this as well.
Everything else is constant - Speed, Fan speed, flow, etc. The print profiles are as similar as can be, since I basically copied the settings from my Orca profile.