They know this doesn’t work. They’ve known for over a hundred episodes. Regardless, invisibility and intangibility are about as solid a defensive concept that the moment you presume the existence of higher dimensions, the only logical step is to use it as a defensive weapon.

And addressing other forms of “phasing” used in the show, and a general flaw that most “phasing” sci-fi uses.

The problem is that any device which allows intangibility, still allows gravity to have a hold on you, and yet also allows you to interact with the physical world enough to run along the surface of a planet must also prevent you from falling, and even be able to lift you. In other words, you could also use it to fly, yet none of the personal level “phasing” devices seem to be designed to do this. If it makes sense to be invisible and intangible, why not let the guy fly, instead of having to climb up 50 flights of steps in some buildings he’s spying in. The time saved would actually decrease the energy requirements of the device as it wouldn’t have to move the person back and forth along the stairs.

Theory 1.02: The dimensional shift in the recent episodes is such that most forms of electromagnetic energy are disjoint from the “phase” the device places matter into. A small part of the spectrum centered around “visible light” is permeable into this “phase”. This could be explained by very precise tuning of the dimensional shifts the device generates, utilizing natural phenomena.

Theory 1.03: The vibrations of matter that generate sounds sensitive to the human ear are likewise transmitted into the new “phase”. This is probably best described as a direct function of the device itself, rather than a natural occurrence.

Theory 1.04: People are not subject to gravity in the “phase” however their minds are so used to the concept of gravity and walking on a solid floor that their subconscious expectations keep them grounded.

My theory is as follows.

Sam knows very little about how the thing works, but since she’s Sam, she’s always explaining things, so she presents an appearance of understanding. She’s throwing technobabble about because, well, that’s all she can do, because the actual mechanism is so far above here that if she didn’t dumb it down, even for herself, it would just be Magic. And that’s the thing, it’s a significantly advanced Technology to be indistinguishable from Magic. Just like with the Ori and the Ancient technology in general. ZPMs for instance are in that realm, but simple enough that we can almost understand how they work, but can’t recreate them. The Stargate itself is one of these, a scientific explanation around something as simple as a Magical Portal between worlds.

Even Rodney does seem to think that she makes sweeping assumptions about a large amount of the technology they are working with.

Still, I personally just think it’s a basic case of bad techno-babble on the part of writers.