If I turn Safe Search off it does (doesn't require age check).

for me, bing refuses to turn off safe search. Lowest it lets me go is "moderate". Google does but doesn't show me pron.

Probably it depends on your geolocation? In a Private Window, after I turn off Safe Search, Google image search shows me everything.

I am in the UK, with UK IP. I get age check on the pr0n websites, but Google doesn't do any age check when browsing incognito and not signed in.

it is very easy to get around it on bing, just go to settings, change region to Germany, then you can switch safe search off. It will ask for age verification, but you can simply click "ok" and that's it.