"O. Szemerényi admits that reconstructions are used to facilitate comparisons, using one word instead of many IE variants, and cites Hermann’s statement that “complete forms (e.g. *deiwos [=S deva-s]) cannot be reconstructed at all, only single sounds, and even these are meant as approximation only”."
January 1, 1970
https://en.wikiquote.org/wiki/Oswald_Szemer%C3%A9nyi