No, those Intersil references use charges stored on floating gate FETs as their reference. Very easy to produce custom voltages but very sensitive to Ionizing radiation, x-rays etc which drains the charge away - just like UV EPROMS.
It's a very different mechanism to other references, to change the voltage of a buried zener would require very large amounts of radiation to damage the atomic structure of their junctions.
EDIT: The problem with the OP's reference probably is humidity - if you check back through the referenced threads about it, it uses an Epoxy packaged REF02 rather than hermetic, making it very humidity sensitive (at the level of precision involved). The claims about its accuracy took no account of that (though a few weasel words have now been added to the listing).