Hello Siva,
Analysis Office is the replacement for BEx Analyzer, not for BEx query designer. If you access the InfoProvider level directly, you would lose out on all the elements that you create in the BEx query layer (restricted key figures, calculated key figures, variables, structures, ...).
In addition you can't use Authorization Variables when accessing the InfoProvider level and therefore the data would not be filtered based on your BI Authorizations anymore.
so yes, best practices is to use the BEx query layer.
regards
Ingo Hilgefort, SAP