Well, we don't know how to build required scientific equipment that will remain operational for more than few decades. Actually, the genetically-modified glowcats mentioned in the article is the closest thing I can imagine that could work over the timespan of many millenia.

Also, I don't see how future archaeologist would not assume anything they find is a "superstitious gobledegook" in need of verifying, if today we do exactly that.

Except that the proponents seem to have forgotten the small fact of evolution. Species evolve. All the time.

Over the course of a 100 century timescale I would expect the glowcats to evolve into quite different species, possibly several such species, or perhaps going extinct. It's anybody's guess, really, and whether they would retain the colour-change genetics is at best nothing more than a rather long-shot hope. Or those genes might evolve to cause the organism respond to other stimuli than radiation.

The only certainty, here, is that such creatures will evolve into something different from what they start out as, so, almost certainly, defeating the original objective.

It's not "superstitious gobledegook", it's how you convey a message without using words only people from our culture and time period would know. Or indeed, without any words at all.

Photographs, diagrams, technological equipment, and everything else, were all proposed in the paper as methods of conveying that information. But there are serious issues with all of them. Very few things will last that long, especially in good shape. And symbols we understand in our culture will have no meaning to them. Even photographs can easily mislead, and as you said, encourage people to explore.

If that's really the only reason, it seems easy enough to circumvent.