I’ve done this myself, and it’s typically because I will want to go through the checkout process to see the total cost of something (including shipping which wasn’t shared on the item page).
I’ll use auto fill to save time and quickly click through to the page that finally shows the full price, then I will back out.
More recently, instead of auto fill I take extra time to type a fake email address just to prevent the “lost cart” marketing emails that were mentioned in the article.
Me too, but the author describes something different.
You say that you "click through to the page that finally shows the full price." So, you are explicitly submitting multiple times. There's a reasonable user explanation that your information would be received by the server.
In the author's example, they're describing something more insidious -- saving the user's information before they submit the form, thereby subverting user expectation.
If I haven't consented to receive your marketing emails or have not entered into a business arrangement by purchasing something, I do not expect to receive emails even if I expect that my information has been received by the server.
I’ll use auto fill to save time and quickly click through to the page that finally shows the full price, then I will back out.
More recently, instead of auto fill I take extra time to type a fake email address just to prevent the “lost cart” marketing emails that were mentioned in the article.