That could be, although I'd guess obscurity in this case might reduce the likelihood of random mentally ill people minor threats, and also reduce the likelihood of being the chosen target of some more capable terrorist threat.

(Even random mentally ill people are likely to have access to firearms, and maybe heavy vehicles.)

Before cloud got big, I used to have a personal physical server colocated at a network facility, in a nondescript commercial building that you had to know was there, and turn off the main street to get to, with no signage I could see. (Also, biometrics scanners, when those weren't consumer things, and a waiting room that seemed to securely lock in visitors, in view of guards.)

I'd previously heard of non-government buildings without signage, for security reasons, so I figured that was it. Rather than not wanting to spend the money on a sign that would make it easier for customers to physically find, increase brand awareness, or raise their prominence in the minds of local officials before whom they might occasionally have business.

And, over time, you hear of other non-government unmarked buildings that are arguably "sensitive", for one reason or another. The ones that personally come to mind, historically that type has been threatened before (by, e.g., people angry at a company that they blame for automating away jobs, people who saw a movie involving blowing up records of bank loans and think that will work in real life, animal rights activists who want to free lab animals (and didn't see that other movie), eco-terrorists, people who are are mentally ill and found something conveniently located to fixate on). Maybe also no need to invite protestors?