I found this on Wiki :
Blastocyte formation begins at day 5
[1]. Differential expression of cells in the morula is thought to be the cause of the lineage divergence of different cell types. For example, the
Oct-3/4 transcription factor is restricted to the ICM, whereas Cdx2 is expessed at a higher level in the trophoblast than the ICM. This differential transcription factor expression is likely to be the result of
positional effect - cells in the middle of the preceding zygote are in a different environment to those on the outside, thus causing differential expression.
So maybe since the embryoblast would be flipped it would mess with the 3 germ layers??? Just a guess