Hi hereusethis,
It would be very odd for you to be able to feel the seam between the split layers on a latex mattress where the layers on each level are the same product and thickness, and the layers are held together with a good quality cover that is tight enough. Latex is quite “sticky” and flexible and the layers generally won’t shift to cause a gap in the area.
For more information about the pros and cons of split layers within a mattress, you can read post #2 here.
Phoenix