Weverything ignores some OPTIONS_GHC flags

When I enable -Weverything, some OPTIONS_GHC pragmas are respected, while others are ignored. For example, with -Weverything, this file

main = print "hello"

foo :: (Num a, Show a) => a -> IO ()
foo = print . show

generates warnings about:

1. missing an export list
2. top-level binding [main] with no type sig
3. redundant constraint [Num a]

If I add {-# OPTIONS_GHC -fno-warn-missing-signatures -fno-warn-missing-export-lists -fno-warn-redundant-constraints #-} to the top of the file and recompile, I expect all warnings to go away. But GHC still reports that main has no signature.

Note that this problem doesn't occur with -Wall. With -Wall, the code snippet warns about the missing signature on main, but when I add the OPTIONS_GHC, the warning goes away. Thus this problem appears to be unique to Weverything.