The article states that small drones must be flown during daylight hours according to the regulations. These drones are flown at night, which means they would be in violation of those rules.
These drones don’t sound like small drones, and the article points out that these are likely over 55 lbs, and therefore subject to different regulations.
The article also suggests that these are not small drones and thus likely not covered under the regulations mentioned.
Also, from the article: "they emerge each night around 7 p.m. and disappear around 10 p.m.". 7-10 p.m. isn't night, it's evening. Yes, in the US it's (probably?) dark by then this time of the year, but maybe they're following some regulation that is defined in terms of time of the day, and not the amount of daylight?
14 CFR § 1.1: "Night means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the Air Almanac, converted to local time."