Sorry, that's why I'm asking the question.
How would it look to fit "X/.{0->Indeterminate}" into Plot3D[]?
A simpler starting point,
Plot3D[Sin[x + y^2] , {x, -3, 3}, {y, -2, 2}]
My interpretation of what you are explaining, which is not working as intended,
Plot3D[Sin[x + y^2] /. {0 -> Indeterminate}, {x, -3, 3}, {y, -2, 2}]
And the application of RegionFunction, which is working as shown,
Plot3D[Sin[x + y^2], {x, -3, 3}, {y, -2, 2},
RegionFunction -> Function[{x, y, z}, z > 0.2 || z < -0.2]]
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