"It's probably not X, but we should consider X as we look at this." and "I feel like this might be X but I'm 50:50 on it." are not anywhere near defamation. You have to get a lot closer to certainty before it's an issue.

And listing out "a possibility but you don't want to dig deeper" is often a good contribution to a conversation.

In this case they worded it badly, but the basic idea of the comment isn't awful.

That someone in the team might not have done it on purpose, but left it for convenience? How does that benefit the debate? I really fail to see any silver lining in doing such speculative comments without any substance whatsoever to back it up.