poor connections don't give you the benefit of a higher cl_interp
The short answer to this is yes, it does actually.
To understand the long answer, I'll give you some insights into what cl_interp does and why you can "stab back in time" with it. I'm gonna assume you know basic networking including ping and the constant communication a server and client have, and what game tick is. You can search it up or ask if you're unsure about something. I just don't want to write a small novel
First of all, you've probably noticed you can click on top of someone's head even though they're not actually there at that time (from the server's perspective) and still hit the person. This is the works of something called "lag compensation". When the server receives your shots, it also gets a bunch of other data like the timestamp of the shot, and because the server buffers a few seconds of ticks. It can go back in time and check if the shot you shot actually hit something. This is the concept of lag compensation and is why people with high ping can effectively "shoot through walls".
Now you might ask "but why does this happen when cl_interp is a high number?", that's a good question. You know that the server only updates everyone's position x times a second? (for tf2, I believe the default is 66) But why are everyone's animations and movement so smooth? That is the works of interpolation. In mathematics, there's a topic called
linear interpolation, which is used to generate extra points between 2 points. This makes games able to smooth movement out without having a ridiculously high tick rate since a bunch of extra points for movement can be cheaply generated, but it requires time. So the client needs to be a bit behind to get the position of everyone and generate these extra points for smooth movement, and guess what? This means a high cl_interp forces you to be a bit behind everyone else just like having a high ping does, and you'll make the server go back in time further while checking your shots.
i doubt someone would put themselves through 2 hours of 2fort at 200+ ping
You'll be surprised
After rewatching the demo, I can't really see anything other than him just having a high ping. Looking at where he's aiming, it looks like he isn't aiming at people but behind them. Combined with the explanation above, I'd say he's as legit as they can be.
Also, for future hacker reports. It'd be nice to have at least 6 different timestamps, a small description of each of these timestamps, and a clear aimbot, wallhack, etc at the start of the report so people checking it out know what the person reported is using. A fine example of this can be found
here.