Hi,
I’m afraid you may need to ask the jetpack team about that. The lazy loader script probably can not recognize items loaded via the ajax request. If there is a programamtical way (by triggering an event or anythin else), then I can suggest a small custom code to trigger the lazy load init.
I could only find the following thread about programmatically rendering asynchronously loaded items to reinitialize jetpack lazy load.
However that solution does not seem to work anymore.