Don’t worry, they have all the data on that, and I’m pretty sure they thought of it.

Fact is that most visits from search engines don’t go very deep anyway. They are allowing a brief glimpse at one page before they start prompting you to log in, and that is likely driving logins while barely shortening those SEO visits, which are not of great value in the first place.

It may come as a surprise but websites often have traffic they don’t want. I recall once my boss noticed there was a non-negligible amount of traffic from parts of the world none of our advertisers care about. He built an endless revolving door of promo offers and directed this traffic into it. It didn’t generate much money but it made the rest of our traffic look higher quality right away.