I tried updating Luma from 6.6 to 7.0 with the Luma Updater 1.4.2 and got an "Update complete" message. However after the reboot Luma is still on 6.6. I checked the version with the Updater as well as holding Select on startup. In both cases the current version is 6.6.
I tried updating manually, downloading the Luma 7.0 7z file and extracting arm9loaderhax.bin. While looking at my files on my SD (over the built-in wifi manager) I noticed that my arm9loaderhax.bin already has the same filesize as the one inside the Luma 7.0 archive. I replaced the file anyway. My n3dsxl booted up normally and when I checked the Luma version it still says 6.6!
One curious thing to note. When I was looking at the files on the microSD I that noticed all the files had an 1.1.1601 filedate.
The Luma Updater worked fine when I was going from 11.2 to 11.3. This and updating the HB_Loader were the only things I modified after the initial hack. Apart from downloading a few games.
I'm using a New 3DS XL with 11.3.