I think they can be detected by some websites as well if it's important enough for them but it's very unlikely that Binance or any exchange for that matter cares that much to go to that extent to catch VPN users.
With the amount of pressure major sites accepting US residents/citizens face, solely using a residential IP address might not be enough. Maybe they're being cautious to avoid false positives for now, hence the numbers of VPN users from the US who could be using the site without problems.