The way I see it, if you want to be pedantic about it (it being a joke photo, so potentially unintentionally reversed by the camera, of a cake which is in 3d space and can be seen in both directions) you might as well do it properly and acknowledge that different orders exist for bits.

Indeed writing conventions are also a good point, however this is not writing. People actually working at bit level are probably more likely to see bits on a scope (so in both LSb or MSb order) than as 1 and 0s written on a piece of paper or a screen.

Indeed, endianness is the order of bytes, my bad. I guess I meant LSb vs MSb

Binary exists in both big-endianLSb or little-endianMSb. In other words, both directions can be valid.

As explained below: Endianness is specifically the order of bytes. I was under the impression that it also implied a specific order of bits but anyways, the correct terms for this discussion is Least/Most Significant bit order.