The "cited by" tab in an article view currently only displays citations from publishers who use the Crossref "cited-by" feature (https://www.crossref.org/services/cited-by/).
While citing references from all journal of JMIR Publications should show up here, citations from other publishers who do not participate in Crossref cited-by may not show up here.
Thus, the references in the "cited-by" tab is not a complete list of all citing articles.