In the case of the 911, the article is wrong as far as technical details. The described 911 tails are all about reducing lift over adding downforce. The first 911 spoiler was the ducktail which reduced lift inherent in the 911 shape. The next was the ‘whale tail’ fitted to early Carrera’s and Non-inter cooled turbos. It added a rubber upturned lip and blurred the line between spoiler and wing. The next was the intercooled turbo tail called a ‘tea tray’ which was taller and bulkier, to leave room for the inter cooler. The tea tray name comes from the upturned sides. So the tail now doubled as lift reducer and intercooled air intake. Confusingly this same tail was also fitted to non- turbo cars. But these are not correctly called a whale tail by the purist.
The later Carreras 84-89 had a similar tail without the upturned sides, which is the one pictured in the article. The turbo tea tray tail lasted until 94.
To add further to the confusion the racing 911s of the 70s grew larger and larger wings to add downforce. The difference was no rubber edging, as pedestrian injuries were not an issue on race cars. The IROC tails look similar to the early road car whale tails, but are much larger.