It is totally messed up random as to when that warning appears. There is no sensible pattern to it at all.
One visit it is there, next visit it is gone. There is no logic to how Google decides this. I’ve not seen the warning today, but did get one yesterday.
I don’t use Chrome, but it is a Chromium based browser. One of the features left accessible is this spyware check. It can be useful when it works. But seeing how it keeps randomly popping up here just because MB links to a few images on that server shows that it is probably just as unreliable on other sites too.