Can you check if approvalScheme variable is set differently after you modified, as there is such possibility in LCM workflows.
But if approvalScheme is set only only owner then technically there should not be any approvals routing to manager. This means that there at some place after you’ve set these variables, they are again getting updated which is why you’re receiving manager approval though you didn’t configure it in aoprovalScheme.
If you can trace it via logs, you can also check the value of approvalSplitPoint at that point.
@amishra4 Please trace in the main LCM Workflow and subprocesses, it should tell you what are the initial values of your variables while launching the workflow and you validate the values of approvalScheme, approvalSplitPoint and approvalOwner to see if the values are as expected or not across LCM main workflow and subprocesses.