Like, did you read past the first sentence? Just because it has less content doesn't necessarily mean there's less to test. It depends on how stuff is working. It depends on how complex it is. It depends on how it's supposed to work. There are a lot of dependencies that will determine how much testing needs to be done. While it certainly seems plausible to need less testing, considering how undertested BFA was for the time it was being tested, I'm hard-pressed to believe 6 months of testing will be enough to deliver a product that was developed with the feedback of the playerbase. At best we might get some adjustments made on arbitrary feedback.
Also, considering that the entire leveling part of the game needs to be retested after the squish, I'm not sure testing needed is less. If they can give like a 1-2 week of a testing period per expansion, we'd need like 2 months at minimum for that alone. Then you have the 5 zones. Each leveling zone should at least have 2 weeks of testing with the maw at least a month. Another two months of testing max level content at a minimum just to iron out any stupid bugs and make sure balance is achieved. I'd be disappointed if we get a testing period that's less than 8 months.