f improve docs

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -956,11 +956,11 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ProbabilisticScorer<G, L> whe
 	/// with `scid` towards the given `target` node, based on the historical estimated liquidity
 	/// bounds.
 	///
-	/// If `allow_fallback_estimation` is *not* set and there is no (or insufficient) historical
-	/// data for the given channel, `None` will be returned.
-	///
-	/// If `allow_fallback_estimation` is set, `None` will only be returned if the given channel is
-	/// not in the network graph (or the provided `target` is not a party to the channel).
+	/// Returns `None` if:
+	///  - the given channel is not in the network graph, the provided `target` is not a party to
+	///    the channel, or we don't have forwarding parameters for either direction in the channel.
+	///  - `allow_fallback_estimation` is *not* set and there is no (or insufficient) historical
+	///    data for the given channel.
 	///
 	/// These are the same bounds as returned by
 	/// [`Self::historical_estimated_channel_liquidity_probabilities`] (but not those returned by