We always called those "sand crabs" and these sand fleas
Those are also called "sand flies," and they actually bite and suck blood and stuff. The things linked really are little crabs - we used to fish with them.
You know, on the page I found it, it says it's a sand fly, but I think you're right. Sand flys are really small, and I'm not sure I've seen a magnified version of them. Looking for other images, I think this is really one and the other is mislabeled:
Totally harmless, if a bit ugly. Not sure why we called them sand crabs when I was a kid and would catch them in a bucket. All they do is try to burrow and hide under wet sand, so when you hold them they try to crawl into your hand. It tickles a little.
We always called them sand fleas within our family. Never really knew what their real name was and hadn't realized others called them sand fleas as well. We often used them as bait for fishing.
I remember digging those up on vacation in Naples Florida in the summers. We used to call them sand fleas too, although I now think that’s not the correct term
In some cultures, sand crabs are eaten as a popular snack, such as in Thailand. They are often prepared via shallow frying in a pan or deep frying in batter. The taste is often described as falling somewhere between that of shrimp and crab. Eating sand crabs presents a risk of paralytic shellfish poisoning and/or infection with Profilicollis parasites.