Nested Search Spec in EAI Siebel Adapter

Hi,
I have a custom code in BS to create the search spec for EAI Siebel Adapter.Query method dynamically. The code creates a search spec like below:

(ICName.Field = 'ABC' OR ICName.Field = 'DEF' OR ICName.Field = 'GHI')

While examining the logs for the output of the EAI Siebel Adapter.Query method we have found that the above search spec have been transformed into one like below:

(((ICName.Field = 'ABC') OR ICName.Field = 'DEF') OR ICName.Field = 'GHI')

Can you notice that the search spec is 'nested'?? I just wanna know the reason behind this nesting.. Is there any way to avoid this nesting??