Unfortunately there is not. The master language would need to be loaded anyway.

What about updating the Metafield directly? That's what I've been trying to do since I put this post up, but my code isn't working. It's not updating the Metafield. It's a PropertyList in case that matters. Here's the code I've been trying to use so far, but it doesn't save the data to the master language record for the product. Am I missing something here?

        private MetaDataContext GetMetaDataContext(string language)
        {
            MetaDataContext metaDataContext = CatalogContext.MetaDataContext.Clone();
            metaDataContext.Language = language.ToLower(CultureInfo.InvariantCulture);
            return metaDataContext;
        }
        
        private void UpdateAllowedMarkets(Product epiProduct, string market)
        {
            IObjectSerializer serializer = _objectSerializerFactory.Service.GetSerializer("application/json");

            MetaDataContext metaDataContext = this.GetMetaDataContext("en");
            MetaClass metaClass = MetaClass.Load(metaDataContext, epiProduct.MetaClassId);

            MetaObject metaObject = MetaObject.Load(metaDataContext, epiProduct.ContentLink.ID, epiProduct.MetaClassId);
            MetaObject metaObj = metaObject == null ? new MetaObject(metaClass, epiProduct.ContentLink.ID) : MetaObject.Clone(metaObject);

            metaObj["PropertyName"] = (object)serializer.Serialize(epiProduct.AllowedMarkets);

            metaObj.DisableSync = true;
            metaObj.AcceptChanges(metaDataContext);
        }

I would advise against using metaobject directly if it is not the last resort. It has very small performance gain and can be very problematic with special types of data - for example PropertyList as yours. If you still want to go that path, your MetaDataContext does not have UseCurrentThreadCulture as false, which is required.