I bought 3 boxes of different sizes of HF squares, 2 boxes had 3 squares, one had 2 squares. All 8 of them are square. If it was just the, "Luck of the draw" then I'd say that I was pretty darn lucky. Or you could say that they are all likely to be square and if you're unlucky you'll get one that isn't. I also have a couple of digital calipers from HF. When checked against my Whiteside setup blocks they both read dead-on. I ordered the squares online but the calipers were from my local store.
I don't have one of the angle gauges that the OP asked about but I did check out a few of them at the local HF store. When checking them against a couple of the squares in the same isle they all indicated that they were accurate. It's unlikely that the squares and the gauges were all off by the same amount and I even tried both sides of the gauges against the squares and they showed the same readings, 90 degrees. I guess you could call this, "The luck of the draw" if you're a pessimist. I believe that this shows that most of the gauges and squares are accurate. I will note that I bought a digital angle finder gauge, (That I couldn't find online) and it wasn't accurate at all and neither were the other examples in the store. So HF isn't perfect, obviously. But I think it's safe to say that for the most part the electronic measuring devices from HF are accurate. I've read other reviews of HF electronic measuring devices here on SMC and I don't recall seeing many, (Any?) that were negative from people who had actually bought and used them. The negative reviews seem to be mostly from people who just assume that if they're inexpensive then they must be junk. This just hasn't been my experience at all.
Bruce