The ones I was thinking of were all in the includes/functions.php file, which is also where the build_datastore(title, data) function is defined. I am fairly sure that they are calling that function.

I don't see any in functions.php, except the function definition.

From a quick grep, it's class_bitfield_builder.php that has a build_datastore with no parameters.

Note, I only checked 3.5 beta2

I haven't taken a look at 3.5 yet, I am only talking 3.0.x here. There really probably is no reason for its existence, especially if they removed those calls in 3.5. Okay, where are the 3.0 devs...? :)

in 3.5 the dev make use of oop more often, so there it might make differences, but in 3.0.x the call without parameters is doing nothing.

let's wait until a dev comes by ^^