Is the PatriciaTree matchGr too strict?

[noughtmare]

I was trying to figure out the time complexity of suc which lead me to the matchGr function.

https://github.com/haskell/fgl/blob/86dc04d2ae9ca73a0923bdc8d78b53bf2f2876c8/Data/Graph/Inductive/PatriciaTree.hs#L146-L158

All the work being done with the bang patterns does not seem to be necessary for the suc function as far as I can tell. I think the strict evaluation could cause the asymptotic complexity of the suc function to change from O(k + min(n,W)) (where k is the number of nodes in the output and n and W are the familiar IntMap variables) to O(n) (because of the clearPred and clearSucc functions). Should this be rewritten to:

 matchGr :: Node -> Gr a b -> Decomp Gr a b 
 matchGr node (Gr g) 
     = case IM.lookup node g of 
         Nothing 
             -> (Nothing, Gr g) 

         Just (p, label, s) 
             -> let g1 = IM.delete node g 
                    p' = IM.delete node p 
                    s' = IM.delete node s 
                    g2 = clearPred g1 node s' 
                    g3 = clearSucc g2 node p' 
                in (Just (p' `seq` toAdj p', node, label, toAdj s), g3 `seq` Gr g3) 

Or something similar.