you got only one possible combination for purple, so it literally doesn't matter
this is for trying to maximize chances when multiple are available and the hybrid takes a combination of 2 different flowers to produce. diagonals are worth more, because typically hitting them properly also hits horizontals as well as diagonals from just about any start point, essentially meaning close to every flower is basically a +1 chance
like take these for example
aba
bab
7 chances for a+b hybrid
aba
aba
8 chances for a+b hubrid
aaa
bbb
7 chances for a+b hybrid
aba
bbb
5 chances for a+b hybrid
abb
bba
6 chances for a+b hybrid
now note how the diagonals play into each in comparision to everything else. the one that hits every possible diagonal comes out strongest, because they always come out as x total flowers on display-2 when done right, whereas verticals will only ever be x/2 rounded down to the nearest whole number, and as a bonus, hitting the verticals also hits every possible horizontal , which is basically an x-2 as well
so like for above, the one thar hits every horizontal+vertical in a checkerboard pattern only ever goes 6/2=3 for verticals and 6-2=4 for horizontals
while for the towers formation that hits diagonals+horizontals you have 6-2=4 for diagonals and 6-2=4 for the horizontals
and then for the one thar sacrifies horizontals but goes for all verticals and diagonals you bave 6/2=3 and 6-2=4 for both verticals and diagonals, respectively
every other combination misses on several chances of one or more of any of this trio, so is more to show how hitting all in multiples is more effective and in what ways