I always used "prompting" to mean "providing context" in genral not necesarlly just clever instructions like people seem to be using the term.

And yes, I view clever instructions like "great grandma's last wish" still as just providing context.

>A given prompt may work poorly, whereas it would have worked quite well earlier.

The context is not the same! Of course the "prompt" (clever last sentence you just added to the context) is not going to work "the same". The model has a different context now.