I know for a fact they are not.
I brought home a few, that were about to be trashed, from work, hoping to plant them outdoors. They survive just fine here in Florida and a lady down the street has a huge one the size of a large bush that looks great every year.
Instead of a watch-dog, I have "watch geese".
Anyone familiar with them will tell you that they are very good watch-critters and very aggressive with strangers...nobody seems to be prepared to deal with "watch geese". In my case, I have three, Larry, Moe and Curly. Larry and Curly are ganders (male) and Moe is a goose (hen/female) and they work as a team/ The moment you set foot inside my front gate, you are under goose surveillance and are being sized up for a confrontation and they will not hesitate to attack with beaks and wing-slaps if they don't recognize you.
Late at night, after passing inspection being permitted to enter my property with six discarded poinsettias a couple nights after Christmas, I set the potted plats outside to deal with the next morning.
By the next morning, the geese had eaten them down to stems and I was preparing for the worst. But both the geese and the poinsettias survived the ordeal...neither turned out to be toxic to the other...case closed.
1. You can call the bluff of an aggressive goose by walking toward it waving your arms. But they are actually very easy to catch and hold. Once captured, they calm right down and just hang out. Until they poop on you.
2. The old adage "loose as a goose" is NO JOKE. We wound up fencing in our dooryard and leaving the rest of the place to the geese because they were pooping on the doorstep.
3. Geese poop while they sleep. (See 2 above)
Would I have them again? In a heartbeat, but they would be prey here (foxes, coyotes), and keeping them through a long Alaskan winter without proper shelter is not an option. I'd have to fence in my deck, though...