I can confirm this.
Server x3650 M4 freshly updated with BOMC, thank you Porto.
Originally I changed the boot order to
1. CD
2. Hypervisor key
3. HDD 0
and _then_ I tried to install using the IBM custom image from CD.
No luck, reboot just after loading imgpayld.tgz
Tried vmware image from CD -> works.
Tried IBM custom image from USB -> reboot just after loading imgpayld.tgz.
So after norbande message, I reset boot sequence to
1 Legacy only
2 CD
3 HDD 0
then installed again from CD, IBM custom image.
Works...
And somehow I felt the CD drive sounding different, so I suppose it was engaged as "legacy" not as "CD". Wild guess.
Anyway, thank you norbande for the strange tip!