Because shoving the words "3D printing" into your proposal is how you get the grant money.
Also, actually doing the work to confirm that the common-sense intuition (that 3D printing glass blocks is kinda dumb) is correct is legitimate science.
The study also looked at casting the blocks. The cast ones were stronger but they noted some problems with their printing process.
They mention a lot of the usual upsides of 3d printing. It’s easy to iterate on a design, easy to modify to a particular need, and allows for geometry that’s impossible for other methods.