SRF optimization question

I am writing a set returning function in C. There are cases where I can
know definitively, upfront, that this function will only return one row.
I have noticed, through happenstance of partially converted function, that
I can mark a normal, non-set returning function as returning SETOF
something, while not utilizing the SRF macros and using PG_RETURN_DATUM,
and it still works as returning one row.

I am wondering, if it is an acceptable optimization that if I know
up-front that a function will only return one row, to avoid all of the
SRF overhead of setting up a new memory context, and a function context
struct, and requiring an extra call to my function to tell Postgres that I
am done sending rows, to simply not use the SRF stuff and interact with
Postgres as though I was not returning SETOF? Is this a sane idea, or did
I just stumble into an accidental feature when I changed my CREATE
FUNCTION statement without changing my C code?

--
UNIX was half a billion (500000000) seconds old on
Tue Nov 5 00:53:20 1985 GMT (measuring since the time(2) epoch).
-- Andy Tannenbaum