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Pennine Hillbilly
Was built right as it broke at the joints not the block, mort should be weaker than the block
It was a poor design, but the fence added to its failure.
Mortar strength is irrelevant, it doesn't adhere reliably to blocks no matter how strong it is and a wall too thin and tall will blow over. Walls don't rely on the masonry being bonded together to resist tension, that's not how they work.