From the daily build language pack LibreOfficeDev_24.8.0.0.alpha0_Linux_x86-64_rpm_langpack_de.tar.gz, 7z tells that the below rpm uses the xz compression method :
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$ 7z l libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.rpm 
[...]
Path = libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.cpio.xz
Type = xz
Physical Size = 16392316
Method = LZMA2:20 SHA256
Streams = 1
Blocks = 28
------------------------------

Next, I extracted the content of this rpm package with the below command :
7z x libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.rpm

This extracts the below file :
libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.cpio

Next I compressed this cpio archive with xz using the minimum and maximum force :
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$ xz -1 --stdout libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.cpio > d-1.xz
$ xz -9 --stdout libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.cpio > d-9.xz
------------------------------

Looking at the size of the files, it seems the rpm uses a low compression force of xz :
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$ ls -lhS *
-rw-r--r-- 1 j j  82M déc.  16 03:39 libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.cpio
-rw-r--r-- 1 j j  16M déc.  16 03:39 libreofficedev24.8-dict-de-24.8.0.0.alpha0-1.x86_64.rpm
-rw-r--r-- 1 j j  16M déc.  16 12:06 d-1.xz
-rw-r--r-- 1 j j 3,8M déc.  16 12:05 d-9.xz
------------------------------

The memory requirement on GNU/Linux in order to use LibreOffice is at least 256MB but prefered 512MB :
https://www.libreoffice.org/get-help/system-requirements/#Linux

The man page of xz tells :
"decompressing a file created with xz -9 currently requires 65 MiB of memory".

So there is no limitation to use the maximum force ("-9") for xz compression inside rpm. 

Users would then be able to download rpm files faster. The servers would save storage and bandwidth. As this is a single compression for many downloads, the maximum compression force for xz would provide an overall benefit.