Thought experiment: build your own VPN company that doesn't log anything and try to convince people like you that you don't do any logging
Unless you're de-facto part of the government like Google and Microsoft - I see no good reason to log anything more than what's legally required.
1. Browsing habits would hardly have an affect on the vast array of data to have an effect on ads presented to you, unless you care about your privacy. Its all target auidence and marketing (look at ExpressVPN or Surfshark. They all offer privacy but never follow up)
2. Their algorithms can avoid showing you ads derived from the VPN if it detects the usage of your actual IP
I don't know if they are logging or not. They say they aren't. The audit says they didn't see evidence that they are.
It's impossible to prove a negative.
actually a very interesting experiment