I doubt this is the BIGGEST pet, or that it is indoors all the time.
I don't think it qualifies as an indoor pet unless the animal is actually housed in the house and stays there to sleep.
Most 'large pets' and 'huge pets' that are in the news, are kept outdoors and in a barn or other housing most of the time, and are housed outside to sleep. They just visit the house once in a while, to be really honest.
Michael Jackson had 4 giraffes he also referred to as 'pets' and each giraffe weighs about 3000 lbs at maturity. A mature buffalo cow goes about 800 lbs, I don't know what a bull goes.
I'm not sure it matters that much, anyway. It's cute to see a big animal wandering around indoors, but it's pretty obvious it needs more room than that. Honestly I think it's a part of encouraging people to get inappropriate or multiple pets that they house inappropriately. I'd rather see a report about a rancher who sets up a wild buffalo refuge, or retrains wild horses to be riding horses.