Custom Report Profile Behavior with historical data

Recently but we had started running a major audit and found all sorts of gaps in the date using custom reports. The reason was as you stated:

custom reports will only reflect data from after the point in time after creation

Now, here's my issue(s) with this:

Is this documented in the product documentation anywhere? Not that I can see nor are many of the behaviors of this product that make me pull my hair out.
You can create a custom report at say 13:00. Then later you can load the report and select a time period of say 7 days. You then sit there wondering why most of the data you would expect is missing. Nowhere in the UI does it tell you the something like 'This report was created on date X. Data will only be reflective of events therafter ...'

I think this is another major flaw in the product and one (amongst others) of the reasons we are moving to Splunk. TheThe fact that custom reports cannot reflect historical data past the time from whence they were created is both is misleading and another reason the product is not up to Enterprise audit requirements.

This is just my opinion. I really like the usability of the product but it falls down on raw accuracy at times.