Regarding the article you shared: I assume Google is making that judgement based on AdWords' conversion tracking, which does not account for offline behavior, but rather tends to track actions like form submissions and calls. That's an incomplete picture for any business with a sales funnel that includes on an offline component (e.g., speaking to a salesperson on the phone, touring a college campus, or coming in for a test drive).
In my experience, customers who click on lower positioned ads might be as likely (or more likely) to fill out the contact form and ask for more info, but they are not as likely to convert into customers. YMMV.