In the PDF, EHR.system_id is a String, in the HTML version EHR.system_id is a HIER_OBJECT_ID.
It seems at some point in the HTML generation that change was introduced and was also migrated to newer versions of the EHR spec, though there is no change log associated with the change in the type.
Looking at the JSON schemas, it seems that modification was taken there too, so the type is HIER_OBJECT_ID.
If this was a mistake in the HTML generated, we are spreading this error all around. If this change was planned, certainly the v1.0.2 HTML is incorrect, but if v1.0.3 does include this change on purpose, we are missing the change log for this.