Here is another approach, some domainers will scrape those portfolios, add them to their CRM/lists, and leech on drops, analyze their profit rates and build profiles on this. Also there is another darker thing that I've never seen anyone talk about, the death of a domain portfolio owner... some will feed on their names after passing away, and having a list of domains from a particular person can gain advantage over someone who do regular backorders (I won't give more details, but I've seen bidding wars just to distract the others from other names). I mean a simple example is the association with the 23&Me database that was leaked (over 25m entries with health issues, names, addresses, predictable behavior, and stuff like that), and I can bet my trashy domains that there are people that own domain names there. This is usually based on whois info gathering and profiling. Now I know that many experienced domainers are taking cautions regarding whois info, privacy or portfolio security, but most of them don't (that can be easily mass-checked), and in some parts of the world, they can become targets, and no, not like stealing, but leveraging their gaps (debt, gambling, health issues, compromising info, and so on), I mean there are hundred of thousands of 6 and 7 figure names out there that are still undeveloped or that they belong to an individual that can be easily identified... just saying.
It might seem like a paranoid fairy tale story, but when it comes to money, avoiding taxes or asset transfer time/simplicity, creativity has no limit or ethics

. Stay safe and secure your portfolios.