Search results are different when using the command-line

On https://www.haskell.org/hoogle/ (link in the readme) searching m (m a) -> m a shows join as first hit.
This matches expectation.

Using the command-line version (hoogle --version -> Hoogle 5.0.17.1, http://hoogle.haskell.org/):

$ hoogle 'm (m a) -> m a'                                               
Darcs.Patch.Witnesses.Unsafe unsafeCoerceP :: a wX wY -> a wB wC
Darcs.Patch.Witnesses.Unsafe unsafeCoercePStart :: a wX1 wY -> a wX2 wY
Darcs.Patch.Witnesses.Unsafe unsafeCoercePEnd :: a wX wY1 -> a wX wY2
Prelude pure :: Applicative f => a -> f a
Control.Applicative pure :: Applicative f => a -> f a
Diagrams.Prelude pure :: Applicative f => a -> f a
CorePrelude pure :: Applicative f => a -> f a
Foundation pure :: Applicative f => a -> f a
CLaSH.Signal signal :: Applicative f => a -> f a
CLaSH.Signal.Internal signal :: Applicative f => a -> f a
-- plus more results not shown, pass --count=20 to see more

Similar results were seen in lambdabot and an entirely different selection on hoogle.haskell.org and stackage.

However, prefixing the search with Monad m => produces saner results:

$ hoogle 'Monad m => m (m a) -> m a' 
Control.Monad join :: (Monad m) => m (m a) -> m a
Streaming join :: Monad m => m (m a) -> m a
Haxl.Prelude join :: Monad m => m (m a) -> m a
Intro join :: Monad m => m (m a) -> m a
Codec.Xlsx.Util.Tabular.Imports join :: Monad m => m (m a) -> m a
Control.Monad.HT repeat :: (Monad m) => m a -> m [a]
Control.Monad.Tools repeatM :: Monad m => m a -> m [a]
Control.Monad.Loops untilJust :: Monad m => m (Maybe a) -> m a
Data.Constraint.Unsafe unsafeApplicative :: forall m a . Monad m => (Applicative m => m a) -> m a
Data.Edison.Seq.ListSeq ltailM :: (Monad rm) => [a] -> rm [a]
-- plus more results not shown, pass --count=20 to see more

Is there any specific syntax that makes the command-line behave more like the web version of hoogle on haskell.org and doesn't require prefixing with Monad m =>?

Start by reproducing the documented web query and the command-line query shown in the issue, including the version noted there, then compare the results with the prefixed Monad query. No files or tests are named, so trace the CLI query handling and search-ranking entry points. Done means explaining or correcting the discrepancy so equivalent queries behave consistently, or documenting the required syntax.