The LinkedIn conversations are grouped by day when added to the contact's profile. The content of the conversation is available in the activity's details and this way, you can have it directly in the timeline.
We use "activities" because it fits the needs of most of our users. In the same way you have the default activities "Phone Call", "Meeting", "Email", you now have activity "LinkedIn Conversation", making it more traceable. All the messages sent within one day are reported as one LinkedIn Conversation in your CRM.