Hi,
If you take a look at the SAP Bundle Patches, some of the patches included cannot be installed in a rolling manner.
What happens "a lot" is that not having a shared OH you end with different patches in the different nodes (you can believe or not, but it happens).
At the end it is your decision, stop the database to install a SBP (downtime) or not do it and have the "risk" of getting the typical answer, your installation is not following the SAP practices and it is not supported, the bug investigation cannot go further.
Regards