I have had a Bunchosia in a protected part of the yard for 2 decades. It really has too much shade where it is, but pretty sure I forgot about in 2010 and it got no protection that year. Don't remember absolute lows, but in 2010 a Mauritius lychee was killed to the ground, Kohala longan killed to ground (grew back as an octopus tree), jackfruit (protected) killed to like waist high, also now an octopus tree.
So I would say in the right spot, 30 is probably (assuming no frost) safe, and like many others, 28 is the magic number (difference between some dieback and she gone)
And the tree for sure is stunted, it is a leggy and sparse, but does make a few fruit now and then, which are good.