Of course not, it's hyperbole to illustrate the point. In the specific cases of Qmail and TeX, the 'bug free' aspect of it however is overblown and a marketing gimmick. It's not that hard (given enough time) to make something bug free, it's a whole different thing when the software needs to evolve at the same time to meet the (changing and expanding) requirements of actual users.
Actually, the reason for not evolving/rewriting TeX is so that old documents can be typeset and produce the same results. I find that an appealing goal.
TeX wasn't born in a night and suddenly appear in binary form. Knuth worked a hell lot to make it clean, make it work and make it fast. At least, for when he wrote it. Go and read The TeXbook