You said it was blatantly obvious, but I simply don't see how it can be obvious at all, much less blatantly so.

Thin depressions in a writing surface, with no pigment, show up constantly because the pressure of something else being written overtop of it travels through to the writing surface below.

I find it much easier to believe that that is what happened here, rather than a scribe writing and doodling with imperceptibly shallow scratches that they can't see even as they're writing. Perhaps I'm missing something; maybe this particular parchment was prepared such that it had a thin, easily scraped off layer of dried surface that would show the marks to the doodler for a few minutes before becoming imperceptible for the next 1300 years. Maybe this was a palimpsest, and the marking had pigment present on the parchment before being scraped off, and only the slight compression that carried through into the lower layers remains. Perhaps there is evidence of it being scraped (surface abrasion, or similar) that would rule out pressure carrying through from an upper layer. Perhaps.

But none of that is in the article, only the statement that it was written with a drypoint stylus (with no mention of how certain that was, or what evidence supported it), so I don't see how it's "blatantly obvious" that the simplest, most mundane explanation is incorrect.

But you find it blatantly obvious. I'm curious as to your reasoning. "I'm going to state that the person above me is missing something blatantly obvious and refuse to elaborate when politely questioned" is a much sillier game to play than "please, explain".