Why is sformat and formattedWrite (appender) allocating GC mem here?

[cc]

And what, if anything, can I do to avoid it?

	string[] arr = ["abcd", "efgh", "ijkl"];
	char[4096] buf;
	char[] res;
	writeln(GC.stats);
	res = sformat(buf, "%s", arr);
	assert(res.ptr == buf.ptr);
	writeln(res);
	writeln(GC.stats);
	res = sformat(buf, "%s", arr);
	assert(res.ptr == buf.ptr);
	writeln(res);
	writeln(GC.stats);

	// Results:
	Stats(64, 1048512, 80)
	["abcd", "efgh", "ijkl"]
	Stats(272, 1048304, 272)
	["abcd", "efgh", "ijkl"]
	Stats(464, 1048112, 464)

I get similar behavior trying to use formattedWrite with an 
appender:

	string[] arr = ["abcd", "efgh", "ijkl"];
	auto formatBuffer = appender!(char[])();
	formatBuffer.reserve(4096);
	formatBuffer.clear();
	writeln(GC.stats);
	formatBuffer.formattedWrite!"%s"(arr);
	writeln(formatBuffer.data);
	writeln(GC.stats);
	formatBuffer.clear();
	formatBuffer.formattedWrite!"%s"(arr);
	writeln(formatBuffer.data);
	writeln(GC.stats);

	// Results:
	Stats(12288, 5230592, 4208)
	["abcd", "efgh", "ijkl"]
	Stats(12432, 5230448, 4352)
	["abcd", "efgh", "ijkl"]
	Stats(12576, 5230304, 4496)

Same thing if I use a format string like "%(%s,%)" rather than 
just "%s".  I'm guessing it's allocating a string first to write 
the contents of the array and then inserting that string into the 
buffer I supplied.  Is there no way to have it skip this step and 
just write each element (plus the joining punctuation, etc) 
directly into the buffer?