Major vendors have realized this as well, and are putting less information in their emails as a result. If you’re my customer and a Gmail user and I send you order details, financial/credit info, any number of things I might know about you that Google might not know already, Google learns that about you from me. Instead, I’m going to send you an email that prompts you to come back to my site or app to get your tracki…
I see no change in this over time, nor do I know why companies would even care that an e-mail provider (including Google) would be able to read that information. I don't think this phenomenon exists at all.
The only thing I can imagine you referring to is companies having the tracking link open to their own page rather than directly to UPS/FedEx etc., but that's for totally separate reasons that you can see from Narvar's marketing.