it is less than 15kb in size
written in assembly
supports structs, unions, inline assembly, gotos, breaks, function pointers
Thus it support more than otcc supported in a fraction of the size
OTCC is <4KB. It's admittedly using tiny names to squeeze under a size limit, but even when you correct for that it's a lot smaller.
(Edit: At the time of submission the link went to https://github.com/oriansj/stage0/blob/master/Linux%20Bootst... with a description of "World's Smallest C Compiler")
So instead of arguing back and forth, it would be more helpful for others reading your comments if you provided full information about the conditions under which those sizes were achieved.
The one that's self-compiled, so it shouldn't vary much if at all.