If Foreign Affairs Office Personnel at public universities in China have told you that Z visas can no longer be obtained by FT's aged 60 or over,I'd expect that to be the case.
As all Chinese teachers in the public sector are compelled to retire by their sixtieth birthday at the very latest,it wouldn't be surprising for said regulation to have been extended to apply to FT's as well.But in the private sector of education in China the aforementioned regulation probably doesn't apply.
However,I feel we need more input.So,I shall be monitoring this thread with more than a passing interest within the next few days.