I wrote:
> Yeah, that's another thing we could simplify if we fixed this problem
> at the source. I think these decisions date from a time when we still
> cared about the speed of fmgr_oldstyle.
BTW, the text you're quoting is from 2007, but it's just documenting
behavior that's mostly a lot older. It's worth reading commit 23a41573
in toto in this connection. I'm not sure if we'd want to revert that
DatumGetBool change or not, if we were to clean up fmgr_oldstyle.
We'd be able to do whatever was cheapest, but I'm not sure what that is.
regards, tom lane