upload of source rpm fails in yum hosted

I uploaded a src rpm to a up to date nexus3 (3.13.0-01 OSS). And it worked fine:

> PUT /repository/Test/SRPMS/7/ngcurl-7.61.0-2.src.rpm HTTP/1.1
...
< HTTP/1.1 200 OK
< Date: Fri, 31 Aug 2018 12:52:48 GMT
< Server: Nexus/3.13.0-01 (OSS)
< X-Content-Type-Options: nosniff
< Content-Security-Policy: sandbox allow-forms allow-modals allow-popups allow-presentation allow-scripts allow-top-navigation
< Content-Length: 0
< Keep-Alive: timeout=5
< Connection: Keep-Alive
< Content-Type: application/x-rpm

But the the content of <hash>-primary.xml.gz is wrong:

curl -k https://nexus.XXX.com/repository/Test/SRPMS/7/repodata/338c845819a87d70703b3ffbbfe763b15bf325c7c017229997621899f7c04b89-primary.xml.gz | gunzip | xmllint --format /dev/fd/0

returns:

<metadata xmlns="http://linux.duke.edu/metadata/common" xmlns:rpm="http://linux.duke.edu/metadata/rpm" packages="1">
<package type="rpm">
<name>ngcurl</name>
<arch>x86_64</arch>
...

Look at the arch attribute, it says x86_64.

I created a local yum repo with createro (0.9.9) on Centos7 (7.5.1804)
With exactly the same rpm, running:

$ createrepo -o $PWD -p $PWD -s sha --database --workers 4

The equivalent file says:

<metadata xmlns="http://linux.duke.edu/metadata/common" xmlns:rpm="http://linux.duke.edu/metadata/rpm" packages="1">
<package type="rpm">
<name>ngcurl</name>
<arch>src</arch>

The arch is now src

A diff after formatting both with xmllint --format returns:

5c5
< <arch>x86_64</arch>
—
> <arch>src</arch>
7c7
< <checksum type="sha256" pkgid="YES">b2a7e8d1a5ff56c9028493ba7103488323578187d4c282e4711199b04509319d</checksum>
—
> <checksum type="sha" pkgid="YES">49d3b8b28b256d65f7cafc94d2a6ed16456bd024</checksum>
17c17
< <time file="1535719990576" build="1535623528"/>
—
> <time file="1535623528" build="1535623528"/>

The only real problem is indeed the arch.