Window sizes can vary widely and if you come from the same IP with the same exact window size (1033x832 for example) then people wanting to track you for ads etc will have a higher degree of confidence that you’re the same person. It’s part of “browser fingerprinting”, which can also include things like the extensions you have installed: https://amiunique.org/
This sort of thing makes me skeptical. It’s like someone saying “there are a lot of bad guys out there, pay me and I will help you dodge them.” But how do you know they aren’t a bad guy and you’re paying them to scam you?
Ultimately the best way for you to maintain security and privacy is to do it yourself. Second best way is for someone you trust to help you. Least good way is to trust some random website. This one seems to be hosted in Malaysia for what it’s worth.
Also in the past I’ve observed that the Google indexing bot will visit a site right after a Chrome user visits the site. So if Googlebot knows nothing about abc123.com and then a Chrome user visits it, then suddenly Googlebot is crawling the site. I wonder if that happens when the Chrome user is in incognito mode?
Honestly no idea why they didn’t just do that to begin with.