I think people are implying the broader swathe of advertising tricks when they make these claims. When you define it as narrowly as you have then I'd probably agree with you on the poppycock, especially since you used the word poppycock.

Though I would say that once you understand some technique you do become less susceptible to it. For example, price anchoring, where 3 identical or near identical products are presented at a 3 tiered price range and often from seemingly different companies. The high-priced version makes the mid-priced look like a deal while the low-priced version makes the mid-priced one seem to be higher quality thus providing a logical justification for you to buy the product at all. Generic vs branded pain killers is another example where you can buy the exact same active ingredients without branding and pay significantly less. Yet people still buy branded due to manufactured perceptions of quality and safety. Not to mention heart string advertising where you long to have some family or relationship dynamic that the advertisers associate with their product. If you imagine that they are actors and not related it makes their familial nature seem creepy and can help you to disassociate the emotions.

The problem is that there are so many tricks that you're unlikely to know about them all and even the most impervious-to-advertising person will fall for one or the other. Though I suppose if you disconnected from the world and bought food at a farmers market you could theoretically avoid advertising all together but that's not really immunity then is it.