Generation of parameter files by DAC at runtime

I was very curious on how actually DAC reads parameterfileOLTP.txt and generates individual parameter files that are passed runtime as a parameter in pmcmd command. I became more curious after I observed that DAC was not taking right values from parameterfileOLTP.txt file. I changed CATEGORY_SET_ID value in different sections to different values as per the documentation but DAC generated one parameter file correctly but the other one was incorrectly populated. It populated one of the parameter file with CATEGORY_SET_ID=27 where as parameterfileOLTP.txt has no such value anywhere in the file.

I am still not very clear on the logic and DAC still maintains default values somewhere thought the value does not exist in parameterfileOLTP.txt. I wonder where. OOB ParameterfileOLTP.txt has additional parameters though the parameters are not defined in the mapping. When I removed those unwanted ones from the file, DAC is passing the correct values. Let me give an example of what I am talking about.

ParameterfileOLTP.txt in \\OracleBI\DAC\Informatica\parameters\input\ has been modified to have $$CATEGORY_SET_ID=1100000023. The entry is pasted here.

[SDE_ORA_InventoryProductDimension_Derive]
$DBConnection_OLAP=PARAM_OLAP
$DBConnection_OLTP=PARAM_OLTP_ORA11I
$$CATEGORY_SET_ID=1100000023

\\informatica\server\SrcFiles has the parameter file is definitely modified (timestamp changed) but $$CATEGORY_SET_ID value is set to ' 27'. DAC is passing the file in \\informatica\server\SrcFiles\SDE_ORA11510_Adaptor.SDE_ORA_InventoryProductDimension_Full.txt in the pmcmd command.

I changed [SDE_ORA_ProductDimension_Full] section to remove mplt_BC_ORA_ProductDimension.$$CATEGORY_SET_ID as the mapping does not a mapplet and the DAC is passing the value that is there in parameterfileOLTP.txt.

I am still searching for the logic but when I remove the ones that are not required, it does work as expected. I will be glad if someone can explain me the logic.