Yes, depending on the bug source. But the bug source might be related to reads. Nobody knows. Splitting the risk across two different vendors / implementations seems to be good insurance.
I mostly handle server appliances and the read-only boot disk is bread-and-butter for anything I do. Bonus points for using initramfs and never hitting the boot disk after the initial boot is completed.
But if you stick to boot SSDs that are read and written to using different makes sounds like a good strategy.
It would of course be hard to avoid read-only flash no matter what you did - both bios and pxe rom from the ethernet card would presumably be read only flash today (that is writeable, but in practice only used for reading).
But if you stick to boot SSDs that are read and written to using different makes sounds like a good strategy.