UUPdump: Feature or Cumulative update?  

If you use UUP dump to grab a cumulative upgrade, it first builds the Windows image from the feature update, then it saves that image to disk, and runs DISM to do an offline update from the CU cab file. Presumably you could stop the command line script it runs when it finishes the initial portion (1909 Feature Update download and image build) and save that file instead. OTOH, If you want to grab a canonical ISO for 1909, you'll want to use the Media Creation Tool ("Download tool now") from the Download Windows 10 page, or the HeiDoc.net Microsoft Windows and Office ISO Download Tool.
HTH,
--Ed--

Purely IMO....

I have created ISOs thru UUPDump with and without including the cumulatives. The extra time and steps required just does not seem worth it. Many extra rebuilding of WIMs to include all the code built in the proper sequence. When using the ISO to do an upgrade or in-place repair/upgrade, accepting the default of "check for updates" during the process is far simpler and quicker. And less error prone. As good as the UUPDump scripting is (and it is well built), there are many more spots where something could go wrong. Unless you have a very good reason for needing a full up-to-date ISO, such as multiple machines to update, I've found it best to stick with the base build and pick up the updates as part of the process.

p.s. - it's considerably larger, too. If the intention is to create a bootable thumb drive, the WIM may not fit in the FAT32 constraints of 4GB.