That is what we did for a long time. If you were to rebuild the same
package at two different points in time with the same set of
dependencies, that would get you different file modification times.
Those would be recorded in data.tar and therefore the rebuilt .deb would
differ from the earlier one. This broke reproducible builds and is what
caused the addition of SOURCE_DATE_EPOCH. Now, dh-strip-nondeterminisim
clamps the modification time of installed files to SOURCE_DATE_EPOCH and
this aspect no longer causes issues to reproducible builds.