It does not report this as available memory to Solaris, which is why there isn't a conflict.
Could you define "report this as available memory" please? Physical? Virtual? In some particular OF node/property?
It's been a while... My recollection is that the /memory node ends up specifying the physical memory that OBP occupies in the "reg" property, while the memory available to Solaris' use is in the "available" property. I found at least one instance where OBP takes 1000.0000 bytes at startup, but that's on a per-platform basis and it's buried in the assembler code, so hard to figure out at a glance.