The iso images are larger than 4.7 gigs after 1803.

There are still "issues" with USB3 devices in general but I do not know why.

I use OEM System Builder DVD of 1809 with an external USB2 Blueray drive and it works on everything from 2006 machines to my new laptop that was built Feb 24, 2019.

https://www.bestbuy.com/site/lg-8x-external-usb-2-0-blu-ray-disc-double-layer-dvdrw-cd-rw-disc-rewriter-black/9243009.p?skuId=9243009

It appears the 1903 Media Creation Tool gives Windows 10 Version 1809 V2 (Build 17763.379) isos and not Windows 10 Version 1903 (Build 18362.1) isos like one might expect...

The Direct Download Links call these Windows 10 version 1809 V2.

Your link shows "Forbidden"  ;)

Up to 1803 works with regular dvd.

1809 64 bit iso's require a DUAL LAYER DVD

because they are larger than 4.7 gigs.

Burning any DVD its recommended to burn at 1X or 2X or 4X max.

8X and faster creates non reliable disks.

1803  get now or forever hold your peace

32 Bit

https://software-download.microsoft.com/pr/Win10_1803_English_x32.iso?t=3a1cc87a-fe89-4d3c-88cb-cc970acfddad&e=1556467744&h=52ba0ddc1d2f6fb8b49a2761d93694b5

64 Bit

https://software-download.microsoft.com/pr/Win10_1803_English_x64.iso?t=3a1cc87a-fe89-4d3c-88cb-cc970acfddad&e=1556467744&h=dc8a70f9e40926909c8976aeb6956ee0

1809 V2 will also likely go away

Windows 10 English

32-bit Download

https://software-download.microsoft.com/pr/Win10_1809Oct_v2_English_x32.iso?t=29b3ec3c-3a2c-43f2-987a-4c4d7029c56c&e=1556477511&h=c17dd094cf0c5c62b8738eed7ad860d0

64-bit Download

https://software-download.microsoft.com/pr/Win10_1809Oct_v2_English_x64.iso?t=29b3ec3c-3a2c-43f2-987a-4c4d7029c56c&e=1556477511&h=09401c7682819da0c5c2d2eec0fd5d0d

Links valid for 24 hours from time of creation.
Links expire: 4/28/2019 6:51:50 PM UTC

Microsoft have removed the Windows 10 Version 1903 Media Creation Tool from their server... It looks like Windows 10 Version 1903 will be released in May at some point.

The links Speedstep posted are time limited... they have 24 hour tokens which will expire, after which they need to be regenerated. However it should be noted that the direct download links for all languages and all older versions of mainstream Windows 10 Builds are available on Microsoft's Servers. You have to however use a third party utility the Windows ISO Download Tool to generates the 24 hour time-limited download links:

https://www.heidoc.net/joomla/technology-science/microsoft/67-microsoft-windows-and-office-iso-download-tool

They added a lot of stuff.

The original 1809 was 4.9 gigs.

The V2 1809 is 5.2 gigs.

Thats 300 megs of extra stuff.

The one with the most stuff before he dies wins.

I don't mind it being larger however the install.wim exceeding 4 GB in the direct download links is problematic for making a FAT32 formatted USB. They should split this into <4 GB files. 

Making it not FAT32 copy-able I believe was intentional to break Rufus installers and people making hacked versions of the installer to bypass activation and adding EI.CFG files etc.

They also are getting all vendors onboard for no more 32 bit drivers so that

driver security enforcement and secure boot are in play.

This also makes MBR no longer applicable and past skylake Legacy booting removed.

This is the path to CLASS 3 UEFI where there is no more Compatibility Support Module CSM.  They want to make expansion cards like video and storage etc like apple where they DO NOT WORK without being from the vendor.

CLASS 3 is the end of the world