Lazy properties in embeddables/composites are not currently supported for embeddables due HHH-10480.
The fix for will call the owning entity BytecodeEnhancementMetadata#isAttributeLoaded for a collection contained within an embeddable, using a property name that is qualified by the embeddable (e.g., grouping.things). The method simply returns false in this case, because there is no lazy property with this (qualified) name.
Depending on how is fixed, Hibernate may need to be changed to call BytecodeEnhancementMetadata#isAttributeLoaded for the embeddable (not the entity) with an unqualified property name.
I made a small change to the fix for so that Hibernate does not bother calling BytecodeEnhancementMetadata#isAttributeLoaded if the collection is in an embeddable.
I will also mention this code needs to be revisited when is fixed.
I also added a couple of tests involving lazy collections in embeddables that shows that things work properly currently, before is fixed.