Add extensive commenting about LegacyLastTick usage

osu.Game.Rulesets.Catch/Objects/JuiceStream.cs

@@ -81,6 +81,8 @@ namespace osu.Game.Rulesets.Catch.Objects
                     }
                 }
 
+                // this also includes LegacyLastTick and this is used for TinyDroplet generation above.
+                // this means that the final segment of TinyDroplets are increasingly mistimed where LegacyLastTickOffset is being applied.
                 lastEvent = e;
 
                 switch (e.Type)

osu.Game.Rulesets.Osu/Objects/Slider.cs

@@ -1,4 +1,4 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
 using osuTK;
@@ -194,7 +194,9 @@ namespace osu.Game.Rulesets.Osu.Objects
                             ComboIndex = ComboIndex,
                         });
                         break;
-                    case SliderEventType.LegacyFinalTick:
+                        // we need to use the LegacyLastTick here for compatibility reasons (difficulty).
+                        // it is *okay* to use this because the TailCircle is not used for any meaningful purpose in gameplay.
+                        // if this is to change, we should revisit this.
                         AddNested(TailCircle = new SliderTailCircle(this)
                         {
                             StartTime = e.StartTime,

osu.Game.Rulesets.Osu/Objects/SliderTailCircle.cs

@@ -8,6 +8,10 @@ using osu.Game.Rulesets.Osu.Judgements;
 
 namespace osu.Game.Rulesets.Osu.Objects
 {
+    /// <summary>
+    /// Note that this should not be used for timing correctness.
+    /// See <see cref="SliderEventType.LegacyLastTick"/> usage in <see cref="Slider"/> for more information.
+    /// </summary>
     public class SliderTailCircle : SliderCircle
     {
         private readonly IBindable<SliderPath> pathBindable = new Bindable<SliderPath>();