When refactoring the alignment types to work with CSS Grid, I couldn't work out what the difference between start/end and flex-start/flex-end was. I came to the conclusion that they were just aliases of each other, and folded them into one. It turns out that this works for Grid, but it is wrong for Flexbox. The difference is:

• flex-start/flex-end are effected by FlexDirection (the RowReverse and ColumnReverse directions flip them.
• start/end are not effected by FlexDirection.

Currently we have variants called Start and End that behave like FlexStart and FlexEnd. We ought to add new variants for this use case, and alter start/end to work as per the spec.

This probably isn't hugely high priority unless someone complains about it because I doubt many people are using RowReverse/ColumnReverse.