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SQL Server Backup Buffers

SQLsasquatch (whose name I now know but I like the handle so much) has a few questions about backup buffers:

I wonder:
-If ‘max server memory’ wasn’t being overridden by a more reasonable target (because max server memory is 120 GB on a 32GB VM), would the behavior still be the same before reaching target?  I bet it would be.
-Is this behavior specific to not having reached target?  Or when reaching target would backup buffers be allocated, potentially triggering a shrink of the bpool, then returned to the OS afterward requiring the bpool to grow again?
-What other allocations are returned directly to the OS rather than given back to the memory manager to add to free memory?  I bet CLR does this, too.  Really large query plans?  Nah, I bet they go back into the memory manager’s free memory.
-Does this make a big deal?  I bet it could.  Especially if a system is prone to develop persistent foreign memory among its NUMA nodes.  In most cases, it probably wouldn’t matter.

Good questions, to which I have zero answers.