Gosh BerylBreeze you have an all yellow Fluttershy - very cool! Congrats - do you have pictures of her?
They never made [or havent yet made] GID versions of FS, AJ or RS similar to how they havent [yet] made metallic versions of TS, RD or RS either. Its always possible they will come along at some point.
The Coming Soon thread shows FS in wave 5 as all yellow as well but thats because its from a promo shot of the set and I am very naughty and havent changed it. As far as I am aware all of the wave 5 FSs were coloured yellow and pink but perhaps there were some early wave errors as per BerylBreeze's comment. Similar to the pink glitter TS in wave 1 before she was corrected to the purple.