The EM field is used both for the function, and the values of that function. (I think it’s actually a skew-symmetric linear operator on the tangent space T_x M at a given point. This can be phrased in terms of a bivector at that point. A “bundle” TM = Union_x T_x M talks about an extended manifold connecting tangent spaces at a different points.) I think it’s entirely reasonable in common language to use “where” to mean “where it’s non-negligible”. Consider that physical objects are also fields. It’s entirely reasonable to ask “where an electron is” even though the electron field is a function of spacetime. Once we’re able to ask the right questions, this becomes a less-useful question, as it only applicable in cases where the field is concentrated. The EM field case just breaks down much sooner.
The EM field is used both for the function, and the values of that function. (I think it’s actually a skew-symmetric linear operator on the tangent space T_x M at a given point. This can be phrased in terms of a bivector at that point. A “bundle” TM = Union_x T_x M talks about an extended manifold connecting tangent spaces at a different points.) I think it’s entirely reasonable in common language to use “where” to mean “where it’s non-negligible”. Consider that physical objects are also fields. It’s entirely reasonable to ask “where an electron is” even though the electron field is a function of spacetime. Once we’re able to ask the right questions, this becomes a less-useful question, as it only applicable in cases where the field is concentrated. The EM field case just breaks down much sooner.