Hi RhysD ,
Conversation (and Smart View) columns differ from Post (and Moderation) columns in several ways. For example, because routing, priority, assignment...are all conversation properties only the Conversation (and Smart View) columns have filters for these.
But they differ in even more fundamental way, and hence names of the columns: the Conversation and Smart View columns shows conversation, where the Post and Moderation columns show posts, whether they are part of a conversation or not. This may seem like "wait, what?" but hold that thought--there are important use cases where this distinction matters.
The data source for both Post and Moderation columns is (simplified) direct from the source channel firehose or similar delivery method. As each POST arrives, it is displayed in a post column, in real time, typically 1-2 secs after delivery.
By comparison, the data source for Conversation and Smart View columns (again, simplified) is the Care data store, after routing, priority, placement into a conversation...have all occurred. This can be 1-2 minutes after arrival, and it is ALWAYS in the context of a conversation.
So how does "lookback" factor into this? First, the Post and Moderation columns are intended to provided a look at each post as it arrives for immeidate review, for example by a Moderator. And recalling the "not a conversaton yet" use mentioned above, looking at Community posts, for example, there are posts arriving from Community board that may not be approved for viewing yet. Since they are not approved, they will NOT be placed into a conversation unitl they are approved. So, the Post and Mod columns can display these so that Moderators can review and approve, at which point they are processed by Care and placed into the appropriate conversation. Spam, pre-mod content, boards with a non-zero resoonse delay, etc. all fall into this category.
Finally, the Conversation and Post data stores are different, as noted above. The Conversation store holds all data for all time for any given customer, with the exception of things like expunged content (think GDPR). The Post store, becuase it is intended to provide a real-time service across the platform, holds content for only a limited amount of time: history is maintained in the Conversation store. Therefore the lookback period is by definition shorter in the Post column: it is currenlty 3 months, and will be extended later this year to 6 months.
BIG NOTE: Manage View, all columns, have ALWAYS been limited to 6 months. So aside from the interim shortening of the lookback (related to a data perfromance enhancement late last year), the real change is that Conversation and Smart View columnsnow have full-history access. This is really important, for example, when asking quesitons like "Which of my Accepted Solutions over five years old still get a lot of traffic?"
Let me know of this makes sense -- a longer explanation but I think this helps to convey the true value of why we made this change, and helps more poeple understand the imprtant differences between the varisou column types and why we have them.