I agree no adult is doing it on purpose.
I think parallels can be useful, but we need to consider which ones are likely to be the most instructive.
i) is school attack the type of thing (in principle) that is susceptible to social contagion? I think the answer to this is unarguably yes.
ii) can doing drills lead to normalisation? That's harder to know for certain. But we know that in other cases promoting remedies and awareness can increase the problem. I think anorexia, suicide, cutting are more similar (as responses to extreme distress, especially amongst teens, who are the main risk group for school attacks), which is why I'd suggest they probably tell us more than lollypop ladies. And there is pretty clear evidence that poorly-communicated or poorly-targeted campaigns against those things does in fact often lead to increaded prevalence.
iii) but what if school drills are always well-communicated and well-targeted, so they don't raise awareness of school attacks, then surely it's fine? That seems unlikely, as we've seen on this board lots of talk of them as attack drills, including cases where the school itself has said that. Even if the school does not, students and parents do.
iv) does doing drills prevent attacks even if they are attempted? (Maybe the above is irrelevant, if these drills foil 100% of attempted attacks). Again, I wouldn't like to bet on anything being 100% effective.
I'm not saying that drills definitely will increase attacks. But you do seem to be saying they definitely won't, but without very much reasoning.
I'm also not saying that drills are definitely not justifiable in any case, just that the above is a concern worth taking seriously.