Hm I just chopped a Tangie that was normal, but my current Sour Diesel seedling is also tri-symmetric :)
Good luck with your plant! Would be interested to know if you notice any differences in how a plant with this mutation has to be cared for compared to a regular one. I started feeding mine higher levels of nutrients and more light earlier than advised because hey, 1.5 times # of leaves leaves translates to 1.5x photon capture surface, thus 1.5x available energy and capacity for nutrient uptake, theoretically (I'm not a biologist, so maybe some of my assumptions are wrong).
like 1