CRIU has so many more features and is so much more powerful that I don't think it's a fair comparison at all to make. You might argue that you could have implemented all of the features on another system like DragonFlyBSD (and in fact I would argue it would've been easier than doing it on Linux) but I don't see why that statement matters. What makes CRIU "unique" is that it does have those features and it is used on production systems for live migrations. I remember there used to be very old Linux tools that did the same thing in the same timeframe as checkpt, but they weren't widely used either because they didn't support any of the things CRIU does.

For example, not being able to restore sockets of any form (such as TCP sockets) is a massive limitation that CRIU doesn't have. userfaultfd allows for CRIU to have a slave process that is used as a source of lazy page loading from another machine (allowing for viable cross-host checkpoint/restore with on paper no downtime). And you can use CRIU to checkpoint/restore entire containers (DragonFlyBSD doesn't have Jails, but it looks like you can't even checkpoint process trees).