This is a pretty good advice: yes it is a pretty good idea to (re)enter job market as a contractor, yes head-hunters do provide value to both job hunters and employers.
About ph.d. working as software developer:
(a) I meet two and both were hardworking but none of them could be considered a good developer. Over years one became barely ok, another left the industry. I suspect my experience is not unique.
(b) try old tech - Intel, IBM, wall-street - again starting as contractor will ease the entrance.