Welcome.
They aren't always ground when done that way. There are certain ways certain things should be done when routing out a board, but they could have done those particular connections any number of ways. Solid, 2 spoke, 4 spoke (what they used), 4 spoke 45 or any way they just felt like. Usually that's done when they are just connected to any large copper plane on the board. Could be power, could be ground, could just be because that's how whoever did it just did it that way. They typically do them like that versus making it a solid connection all the way around the pad as that takes quite a bit more heat to solder a solid layout versus that spoke pattern, then there's still plenty of trace for the connection and current to flow, though a solid connection would handle a lot more current versus a spoke connection, but not a single thing in the controller would benefit from that. In this case it's also a multi-layer board, so there could also be internal connections to those ground spots as well.