Gizmo always talks in the 3rd person As to why? Only Gizmo knows.
However, the general consensus on the forums is what Gizmo mentioned. The rationale is that currently PVP matchmaking is based on a lot of things, but your defense team seems to be part of it. So in setting a defense team with a lower Team Power score nets you easier opponents to invade. It's unclear whether this is intended behaviour for the matchmaking code or not (I'm guessing not, but it's how it works at the moment), however the reason the devs had to "nerf" single troop defenses is because too many people were using them, and it was getting to the point that people could just refresh their opponents and only fight single troop opponents for easier wins (http://community.gemsofwar.com/t/single-troop-defenses/24808?u=ozball). Now you can't set single troop defenses, but people still try to field the weakest defense they can for the reasons mentioned above. As to how long it will be before the devs act and fix the PVP matchmaking in general I'm not sure, but for now those are the reasons people are doing what Gizmo talks about.