I think this is an outrageous abuse of the term “dark pattern” from people who want to be angry more than they want to think. The website mentions repeatedly what the pricing model is, and the operation is “we show you exactly how much value you would get from paying, and then you can decide whether it’s worth it to you.” That’s as honest and plain as business can get: Plenty of people don’t have many/any files which would benefit from APFS COW snapshots and for them paying before the scan would be a ripoff.

We used to call products like this trials or trialware. There was always clear verbiage on the site attesting to the fact that the product was not free but that you could download it for a trial to see if you liked it before paying for it. But I suppose this doesn't even really offer a trial as it doesn't do anything at all until you pay.

Here, the first mention of any kind of cost to this software is ~1/8th of the way down the page when you're met with Q: How do I pay for Hyperspace? which litteraly states that it's a free download that doesn't do anything unless you pay them, meaning that it is not free in any sense of the term.