I have Lychee trees. I wouldn't compare them to the Strawberry Trees. I wouldn't go as far to say it taste like a grainy plum. Of course if you are forging unripe fruit off someone's ornamental tree that's probably what it will taste like. Now if you care for your tree like we do our fig trees. Now that's a whole different package. I kid you not this fruit actually taste like figs with a hint of plum and peach. Not extremely sweet but just subtle enough on the taste buds. The trick is to pick it ripe. If you pick it green or yellow then that will most likely give you a bad grainy experience. Just think of figs, plums, pomegranates and persimmons when you pick them unripe. You see just like figs they won't keep fresh if you store them for to long. This is why they are not a commercial fruit. No money to be made. Basically same scenario. You have to pick them when they are ripe of the tree to be able to enjoy and appreciate the fruit. If you Google more information on the net you will see all the benefits it has to offer. Some cultures swear by it's medicinal properties. Others use it for baking, jams and beverages. We have kept our tree for years. This tree is not appreciated by those who have not grown it. The Irish, Portuguese and great part of Europe valued its fermentation qualities. Just for it's ornamental qualities it is well worth having it in your collection. Gorgeous flowers and fruit just in time for the holidays.
Take a look at this article if you want some honest history on this tree.
http://www.treehealthcare.co.uk/strawberry-tree-history/
Imagine how ridiculous it would sound if your heard someone say figs taste hard and bitter but my bunnies love them. :)