They're different games with different genres, the dev has stated they are different games, and the dev has stated that he will continue Section 7 when this game is done. This is not hearsay, this is stuff he has said in writing, and you can see that if you join the discord and read the FAQ (he doesn't often respond to DMs because of spam, though he can be found chatting on the server itself quite a bit), or become a patreon and read his patreon posts.
And yes, it does hurt his development, because you forget that a lot of people here don't bother to account for the fact that a test version is going to be incomplete, buggy, and lacking in content compared to a full version or even a demo version, then they complain, and then people who haven't played the game get the wrong idea, etc etc. I know it's a pirate site, it's a pirate site I use on the regular, but it's also a pirate site with forums and review features, and that means people can greatly influence other's opinions just with comments and reviews. It's a double edged sword, I suppose.
The reason for private testers is explicitly to test ideas, features, and mechanics to make sure they fit the game and function well, so that the demos and later the full version are polished and leave a good impression where a test build might not.
As an aside, onto your comment about Section 7 being easier to develop... not necessarily. Many of the aspects of Section 7 would need to be more complex, particularly regarding environment (sound and lighting notably), AI intelligence and behaviours (due to their need to hunt the player, respond to stimuli, and interact with the environment), inventory management (at least, I believe. We haven't seen the inventory for PER yet), and maybe even world design, due to the need for interconnectivity and complexity compared to open fields and cliffs as seen so far in PER. Just speculation (I'm no game dev) but I wouldn't be sure S7 is much less complex than PER
