If I bought one unit of Apple stock, if the USD loses value, it doesn't effect the value of my apple stock. It now takes more dollars to buy an Apple share, but my Apple share is still 1/100 of Apple. Currency devaluing makes it look like I'm making money because the share price rose, but I'm not. To be fair, I'm making money but the total value has not changed. I can trade that Apple share for more dollars now, but I probably can't trade it for more bread or other "assets".
If the currency loses 8% of its value, one would expect the share of Apple stock to cost 8% more currency. So if my "return on investment" is 4% but the currency is worth 8% less, that means Apple's value has changed in addition to inflation happening. My stock lost value there. Not due to inflation, but due to Apple being valued less by the market for some unknown reason.
The impact is still disproportionate. While I lost 4% in your example, a pleb holding cash lost 8%. And plebs have a greater share of their net wealth in cash.