In a normal mode, if accessing camera/mic in safari, it will show a dialogue to grant access. (Since full-screen mode only works in iPad, as of the time of development when I tried before) This is different in iPad in full-screen mode, it just does not show the access dialogue as at all. I have tried iPad IOS 12.0.1 and 12.3 beta. Both have the same behaviour.
<rdar://problem/49855313>