IPTC is a legacy format that has been abandoned by the IPTC 10 years ago.
IMatch imports existing legacy IPTC and fills it into the IPTCCore and IPTCExt namespaces in XMP, as required by the IPTC and the Metadata Working Group.
No legacy IPTC data is created by default for files which don't have legacy IPTC data - also in accordance with MWG and IPTC recommendations.
If a file has legacy IPTC data, IMatch imports and also updates it.
The Default Metadata panel in IMatch does include some standard tags from the IPTCCore namespace, e.g. title or copyright. Many legacy IPTC fields have been deprecated and are no longer standard of IPTCCore or IPTCExt in XMP. If you still have a workflow based on legacy IPTC data, I suggest you reconsider and switch to a more robust and modern XMP-based workflow. This is also the default in IMatch 5.
For details about all this, see the Metadata help topics in the IMatch Help System.