[c0nsumer]

I suspect they are meaning because it's uniform you can easily find the studs through it and fasten things directly into them.

An uneven wall material (plaster on lathe, or even plaster on drywall as we have in most of our house) can be quite a hassle to find the actual timbers/studs behind.

[hedora]

Modern plaster has the same properties, and works well with stud finders.

On a related note, if you can find a strong rare earth magnet, you can use it as a stud finder. It'll be attracted to the nails used to hold up the drywall / plaster backer boards. They sell purpose built ones with felt backs + built in bubble levels if you want to get fancy.