Generally, I can see your point, and you may be a good teacher. Age restriction rules are enforced differently in different provinces of China. Guangdong province is quite strict in that respect while in Jiangsu province a Chinese key university ( elite unis - whatever that is in a Chinese context) sent invitations to employ me several times because they could not find any other qualified person. I was 63 y/o then. So, you should ask the question which province is less strict and more "flexible" in terms of these age restrictions. Plus, the better qualified you are, the higher is the chance that they would allow you to work there legally regardless of any age restrictions.

If you have your profile on display on the Internet it's possible to get many 'invitations' from schools when you're 75, but that's only because they haven't really read your profile. If you then reply to the invitation they will look at your information more thoroughly and either ignore you or say they are sorry but you're too old or you're not suitable for some other reason. No these speculative contacts from employers don't mean a thing. They are not really invitations- only invitations to reply for further consideration. Degreeless folk also get many invitations, but if they replied, if they are not ignored, they are likely to get a reply saying, no ,you don't have a degree.