yeah i think i was really lucky but i DID breed redwheat from two wheat definitely
there is no way that i bred it from anything else because do not have much space to do agriculture so i only have four 3 by 3 by 3 fields and to get my supply of food from this i only breed wheat so it was definitely wheat + wheat (Tier I + Tier I)
so as you quoted they have trouble" but i know now, that it's not impossible, so i think we should do further research on this
ps i don't think that we undestand the complete mechanics of agriculture already ...