Why does this building do really?

It gives percent bonuses on loyal and devoted. Only allies are loyal or devoted. So, does it give bonuses to my allies or does it give me bonuses on my agreements with my loyal/devoted allies, or what's the deal?

When I search for other posts about the Endless Research Park and EndlessWorld I found a year old post showing it was giving bonuses to happy and exstatic planets. But that was obviously changed for some reason.

Loyal and Devoted refer to your empire's happiness. It is shown on the left side of the F1 screen. If most planets are happy, your empire is loyal; if most planets are ecstatic, your empire is devoted.

Your right!

I'd suggest a little more player help there though: Like say "on devoted empire" instead of just "on devoted" and maybe something in the text to help you understand the effect is on your own empire.