Reports were possible in FlexCel 3 via TXlsxAdapter, but not natively in FlexCel 6. Now FlexCel 6 has its own native reporting engine, and you don't need to install FlexCel 3 for reports.
The new reporting engine in FlexCel 6 is also much more capable than the one in FlexCel 3, it allows for example to run a report from a TList<T> besides from a TDataSet. It also allows expressions, like <#if(<#a.name> = "John";<#format cell(red)>;)>. It also allows you to write the SQL directly in the template, to run reports that grow in columns instead of in rows, and a really long list of etc.
Make sure to take a look at the document "migratingfromflexcel3.pdf" and also at the more than 30 new demos in reports. (to look at the new demos, just run maindemo.exe and select the one you want to see).
For the scope of this release, this should be a 7.0 for FlexCel VCL, since the reporting engine is one of the 3 pillars of FlexCel: Xls/x engine, Rendering Engine, Reporting engine. But since the new reports were already available in FlexCel 6 for .net, and we want to keep the same number, this is "just" a .1 increase.
In fact, FlexCel 6.3 was a major release (With html5 support, svg exporting, and winphone/winrt support for .net). And so was FlexCel 6.5 (with pdf/a support and a completely renewed pdf engine). And for VCL 6.6 is again a major release. We should be at FlexCel 9 just from those :)