I'm personally not sure what you are talking about, heh :) You mean the AO shader with which you can use AO to get dirt and similar effects going? Or are you referring to AO while rendering?
If its the latter, well, Corona doesn't have any "fake AO" - its all pathtracing and UHD caching so it should behave like it does in reality. Nothing to disable because nothing is there :)
If you want to generate an AO multipass element then you can do that via the Corona Multi-Pass menu and add it to your image in post-production.
Sorry if I'm not particularly helpful but I wanted to give it a shot.