They are for all 1809 aka 17763.1 based sku's. You can check the update.mum file inside the cab, for applicability.
You only need Dynamic Update for upgrade both Flash updates are the same version, they just added the missing EnterpriseS/Server editions other editions don't need the 2nd release
Interesting. Does this have something to do with problem we had when integrading Flash for 1809 using W10UI_5.2? So M$ "resolved" that issue? with re-releasing Flash?
MSFT just didn't put enterpriseS and SN in the applicability list of the first released version*, now they re-released it with enterpriseS and SN onboard. *: https://forums.mydigitallife.net/threads/windows-10-hotfix-repository.57050/page-329#post-1471380 & https://forums.mydigitallife.net/threads/windows-10-hotfix-repository.57050/page-329#post-1471386
A (maybe stupid) question: I'm currently using W10UI to integrate updates into install.wim, but do I also have to integrate them into boot.wim? Or is this file completely different and needs to be left "untouched"? Thanks
You can integrate the updates (SSU/CU and sometimes a Dynamic Update (DISM) into winpe images, boot.wim and winre.wim. If you don't know how, use W10UI_5.3 by @abbodi1406
Nope, only the SSU is released publicly and the 17763.55 CU + the flash update were publicly released, the CU for 17763.104 was IP only.
I seriously think that one good build a year for windows 10 is ok with periodic security updates /patches. Renaming build numbers with no major change in kernel is point less.