SteamInventoryDefinitionUpdate_t callback never triggers after SteamInventory.LoadItemDefinitions()

[ScarlettHoefler]

After calling SteamInventory.LoadItemDefinitions();, our registered callback for SteamInventoryDefinitionUpdate_t never seems to get called.

A rough snippet of our code:

public class SteamPlatformStore : IPlatformStore
{
//...
    private bool _steamInventoryDefinitionsLoaded = false;
    private Callback<SteamInventoryDefinitionUpdate_t> _onSteamInventoryDefinitionUpdate;

    public void Initialize()
    {
        if (!SteamManager.Instance.Initialized)
        {
            Debug.LogWarning("[SteamPlatformStore] Steam not initialized; cannot initialize SteamPlatformStore");
            return;
        }
        
        _onSteamInventoryDefinitionUpdate = Callback<SteamInventoryDefinitionUpdate_t>.Create(OnSteamInventoryDefinitionsUpdated);
        Debug.Log("[SteamPlatformStore] Loading Steam item definitions...");
        SteamInventory.LoadItemDefinitions();
        
        IsInitialized = true;
    }

    private void OnSteamInventoryDefinitionsUpdated(SteamInventoryDefinitionUpdate_t param)
    {
        Debug.Log("[SteamPlatformStore] Steam item definitions loaded!");
        _steamInventoryDefinitionsLoaded = true;
    }

//...

However, in spite of this Callback never triggering, we are able to successfully fetch data with SteamInventory.GetItemDefinitionProperty(...), so this isn't a blocker for us. However, it does add some fragility/complexity in that we're unable to check if item definition data is finished loading and ready ahead of time before trying to access it.

We are using package version 2025.161.0 due to some issues we had with the current latest version (2025.163.0), but none of the patch notes for the releases between imply anything would have changed with this. We are using Unity version 6000.3.13f1 (Unity 6.3 LTS)