What they're actually tracking tends to be the fact you've searched for $productcategory (whether you bought or not)
In theory since they also have purchase data their 'purchasing intent' categories could exclude people who have subsequently purchased from $productcategory for products which are substitutes (but definitely not products which are complements/consumables/collectibles etc, because someone who has just bought guitar/fishing accessories isn't just likely to buy more guitar/fishing accessories again in future but a lot more likely to than the average person), and yes they could even make guesses about whether somebody is likely to want more than one office chair based on whether they're purchasing as a business or an individual. But in practice it's not easy when they've got a product inventory that's so enormous, complex and dubiously-labelled even the basic product search doesn't work that well, and most of the time the vendors are paying them to show the ads anyway. And still wouldn't be perfect (ironically I seriously considered buying two different vacuum cleaners for different use cases this week!)
It's surprising how bad basic targeting is, like when Facebook allowed ad targeting by sexual orientation but even dating websites spent vast sums without bothering, so its unsurprising subtle distinctions about which buyer types only need one of which office accessory are often missed.
In theory since they also have purchase data their 'purchasing intent' categories could exclude people who have subsequently purchased from $productcategory for products which are substitutes (but definitely not products which are complements/consumables/collectibles etc, because someone who has just bought guitar/fishing accessories isn't just likely to buy more guitar/fishing accessories again in future but a lot more likely to than the average person), and yes they could even make guesses about whether somebody is likely to want more than one office chair based on whether they're purchasing as a business or an individual. But in practice it's not easy when they've got a product inventory that's so enormous, complex and dubiously-labelled even the basic product search doesn't work that well, and most of the time the vendors are paying them to show the ads anyway. And still wouldn't be perfect (ironically I seriously considered buying two different vacuum cleaners for different use cases this week!)
It's surprising how bad basic targeting is, like when Facebook allowed ad targeting by sexual orientation but even dating websites spent vast sums without bothering, so its unsurprising subtle distinctions about which buyer types only need one of which office accessory are often missed.