Answer
Not necessarily — IFS's general policy, stated in the technical guide, is that once a major Oracle database version (like 19c) is certified for a given IFS release, the latest available Release Update (RU) revision of that certified version is supported too, even if that specific point release isn't individually named. So a newer RU of an already-certified major version is generally covered by that same certification, rather than needing its own separate, explicit sign-off — worth confirming against the current technical guide for your specific IFS version, since this general policy is what's stated there rather than an exhaustive list of every individual patch level.