That's not what a FOTM is, newfag. A FOTM waifu is a character of typically obscure origins (background character, maybe not even a speaking one. Or commercials like e-surance girl) that attracts a lot of concentrated artwork creation over a short period after its brought to /co/'s attention but is typically not sustainable either due to lack of material or it simply does not catch on. Such curiosities lack a sizable fanbase to draw, commission, or otherwise bring attention to that character for any long term period of time, they might spring up in a discussion from time to time or you might find them in some haremfag's waifu chart but otherwise they're forgotten after a short period, hence flavor of the month. A good example is that pink haired kellog's cereal girl, she was a brief FOTM then went completely awol for years before someone brought her up again recently.
Miko is a main character on a show that, while not likely to live beyond this year barring a miracle, still has an entire season's worth of material. Jackie has been a popular waifu for years now. I'm not familiar with the fanbases of Le Tard Jester or RWBY shit but they seem to have pretty sizable and sustained followings themselves.