I have the same problem with healthchecker on Exchange 2019 as I do with 2016. Not at all sites or servers, seems random. Healthchecker is v23.04.04.1055, latest as of right now. Shows KB5030524 is installed, build number is AugSUv2 yet still reports the SU is not the latest. No other issues are reported:
Generation Time: 08/29/2023 18:22:13
Version: Exchange 2019 CU12
Build Number: 15.02.1258.025
Exchange IU or Security Hotfix Detected:
Security Update for Exchange Server 2019 Cumulative Update 13 (KB5026261)
Security Update for Exchange Server 2019 Cumulative Update 13 (KB5029388)
Security Update for Exchange Server 2019 Cumulative Update 13 (KB5030524)
Not on the latest SU. More Information: https://aka.ms/HC-ExBuilds