Rav Heinemann only said that about it being permissible to see a doctor of the opposite gender (and him physically handling the patient) and it not being chiba. He did not apply it to any other situation such as handshaking.
You can check this with Rav Heinemann. (Or with any talmid of Rav Ahron.) You also provided no source for your claim that he was lenient in the face of virtually universal prohibition by the gedolei haposkim.