When gardening was first introduced it was thought some crosses could only be obtained by planting in a specific order. There wasn't much testing done so it was incorporated into the site design and left alone for a while.
Over the past few months there has been extensive testing (and indirect testing) of crosses that were thought to be one-way only. Every single result has proved to be a two-way cross (most of which has been logged on the Discord channel).
After getting a bigger and bigger data set of the crosses it became clear that one-way crosses were either a thing of the past and something the devs patched in...or one-way crosses never existed in the first place (due to incomplete cross results and/or user error).
This will serve as the official announcement. It doesn't really affect much in the overall scheme of things in regards to efficient gardening but make things a bit more straightforward when crossbreeding.