The practical difference between 4 PIF and 400 PIF is non-existant. At these error levels, variations are meaningless and should be expected. Even scanning the same disc in the same drive several times can produce similar variations.
Total error counts are not an absolute measure of burn quality, and never have been.
That said, it is true that each generation of Liteys have reported slightly fewer errors than the previous generation. You can make any assumptions you like from that fact.