The phone decides for each settings-section (e.g. telephony, identities, ..) whether it replaces the existing settings-section or if it merges the provided settings with the existing ones.

When patch is set to false then the settings-section is replaced.

  <configuration patchDefault="false">
    <keys version="1.8.8"><!--replace because of patchDefault="false"--></keys>
    <identities version="1.8.8" patch="true"><!--merge because of patch="true"--></identities>
    <telephony version="1.8.8" patch="false"><!--replace because of patch="false"--></telephony>
  </configuration>
  <configuration patchDefault="true">
    <keys version="1.8.8"><!--merge because of patchDefault="true"--></keys>
    <identities version="1.8.8" patch="true"><!--merge because of patch="true"--></identities>
    <telephony version="1.8.8" patch="false"><!--replace because of patch="false"--></telephony>
  </configuration>