Windows: Inconsistent hReady behavior between POSIX and native IO managers

While debugging a Windows-only issue with the sbv library (see https://github.com/LeventErkok/sbv/issues/644), it was discovered that the hReady function behaves inconsistently between IO managers on Windows. The following two programs attempt to minimize what goes on when sbv communicates with an external process:

-- Producer.hs
module Main where

import System.IO

main :: IO ()
main = do
   s <- getLine
   putStrLn $ "Responding to: " ++ s
   hFlush stdout

   _ <- getLine
   pure ()

-- Consumer.hs
module Main (main) where

import Control.Concurrent
import System.Environment
import System.Process
import System.IO

main :: IO ()
main = do
  args <- getArgs
  pgm  <- case args of
            [p] -> pure p
            _   -> error "Pass the path to the producer executable"
  (inp, out, _, _) <- runInteractiveProcess pgm [] Nothing Nothing

  hPutStrLn inp "Hello"
  hFlush inp
  threadDelay 1000000

  let collect = reverse <$> go ""
      go sofar = do isReady <- hReady out
                    if isReady
                       then do c <- hGetChar out
                               go (c : sofar)
                       else pure sofar

  s <- collect
  putStrLn $ "Producer says: " ++ s

First, compile these programs with:

$ ghc-9.2.7 -fforce-recomp Producer.hs -rtsopts
$ ghc-9.2.7 -fforce-recomp Consumer.hs -rtsopts

Next, run the following command, first using the POSIX IO manager:

$ ./Consumer.exe ./Producer.exe +RTS --io-manager=posix -RTS
Producer says: Responding to: Hello

This is the expected result, and this is what happens on Mac and Linux as well.

Now run the same command, but with the native IO manager:

$ ./Consumer.exe ./Producer.exe +RTS --io-manager=native -RTS
Producer says:

This time, it simply prints out Producer says: without any further output. This seems to indicate that the behavior of hReady differs with the IO manager, which is not what I would expect.

I used GHC 9.2.7 above, but I get the same results with 9.4.4 and 9.6.1-alpha3 as well.