ScriptedImporter and ScriptableObject

I have an issue with ScriptedImporter and ScriptableObjects where a ScriptableObject imported through a custom ScriptedImporter appears empty when referenced in another object.

Here is the ScriptableObject class that is imported which is basically a container of Vector2:

 public class SampleSequences : ScriptableObject
 {
     public List<List<Vector2>> Sequences = new List<List<Vector2>>();
 }

The ScriptedImporter is in charge of reading an asset file and filing in the Sequences member with the Vector2s, as such:

 [ScriptedImporter(1, "sseq")]
 public class SampleSequenceImporter : ScriptedImporter
 {
     public override void OnImportAsset(AssetImportContext ctx)
     {
         SampleSequences sampleSequences = ScriptableObject.CreateInstance<SampleSequences>();
         var lines = File.ReadLines(ctx.assetPath);
         var culture = CultureInfo.GetCultureInfo("en-US");
         Vector2Sequence currentSequence = null;
 
         foreach (string line in lines)
         {
             if (line.StartsWith("//"))
             {
                 if (line.StartsWith("// Sequence"))
                 {
                     currentSequence = new Vector2Sequence();
                     sampleSequences.Sequences.Add(currentSequence);
                 }
             }
             else
             {
                 var tokens = line.Split(new char[] { ' ' });
                 var sample = new Vector2();
                 if (!float.TryParse(tokens[0], NumberStyles.Float, culture, out sample.x))
                 {
                     DestroyImmediate(sampleSequences);
                     return;
                 }
                 if (!float.TryParse(tokens[1], NumberStyles.Float, culture, out sample.y))
                 {
                     DestroyImmediate(sampleSequences);
                     return;
                 }
                 currentSequence.Add(sample);
             }
         }
 
         ctx.AddObjectToAsset("MainAsset", sampleSequences);
         ctx.SetMainObject(sampleSequences);
     }
 }

When I break in the OnImportAsset method, I see the SampleSequences object is properly filled with 100 elements in the Sequences property. Now the other ScriptableObject referencing this "imported" SampleSequences object goes like this:

 [CreateAssetMenu(fileName = "Data", menuName = "ScriptableObjects/Config", order = 1)]
 public class Config : ScriptableObject
 {
     public SampleSequences SampleSource;
     public int SampleSequenceIndex;
 
     private void OnEnable()
     {
         var sequenceIndex = SampleSequenceIndex % SampleSource.Sequences.Count;
     }
 }

I created an instance of this Config object through the asset menu and set its SampleSource property to the imported SampleSequences object. So, on paper, I would assume that my Config object should have a reference to a SampleSource object with 100 elements in it. Unfortunately, when I put a breakpoint inside the OnEnable() method of the Config object, I see that there is indeed a SampleSequences object in the SampleSource property but with 0 elements in it! What am I doing wrong?

PS: I've also tried calling directly AssetDatabase.LoadAssetAtPath in the OnEnable method of the Config object but get the same SampleSequences object with empty elements.