Nobody is "locked out" of their projects. When your subscription expires, it will be the same as opening a project in the free edition of C2. You can still open it and run it, you can see your events, open sprites and extract your artwork and animations, and even preview it to play it. The main thing you can't do is edit it or export it. You can see exactly how it works by opening Kiwi Story in the free edition of C3. It exceeds the free edition limits but you can still look around the project, access all the artwork and assets, and preview it. Your own projects would work similarly if your subscription was not renewed.
I think people talking about being "locked out" or "holding projects hostage" are deliberately trying to make it sound worse than it is. It's the same as going back to the free edition of C2.
Exactly as you say — When the subscription expires you will be able to open a project, look at the events, extract animations and sprites etc. But you wont be able to edit your game. And you wont be able to export it. You wont be able to do anything meaningful or useful with it. You wont be able to progress your project.
So... do I really own my work under these conditions? The moment my subscription lapses, I can't do anything with my project.
This is fundamentally different to how C2 works. I can open a project from a couple of years ago and start working on it straight away because I own a copy of the software. Same applies to Photoshop CS6 and earlier. I can open any files from any projects I worked on in years past with no worry about being paid up, because I own a copy of the software.
If I create a project in C3, then allow my subscription to lapse, I can't do anything with it. So I think it's not far from the truth to say your project is 'held hostage'. C3 users will certainly be 'locked out' from editing and exporting their own work.
You seem to acknowledge the the truth of those statements in your own post, while at the same time saying it's being made to sound worse than it is.
I think it's exactly as bad as it sounds: You wont be able to edit or export your own work that you spend hours/days/weeks creating unless your 12 month rental is paid up.
Please consider making a pay once option available for C3. I'd buy it!