Is this a twisted PR stunt?
I'm no financial wizard, but this seems ridiculous to me.
The investor spent $257,040 buying their 21,000 shares at $12.24 each. Today the AMD share price is up (again), and the value of those 21,000 shares currently stands at $12.18 each, or 6 cents less per share with a total value of $255,780. This is only $1,260 less than the initial purchase price, and considering AMD's share price is on an upward trajectory right now I see no reason at all to take any legal action? If this legal action has any effect at all it would only lower the share price and make the investor's own financial situation worse!? If the aim of the investment is to make money, rather than make AMD look bad, then this is a totally pointless endeavour at best and at worst financially damaging to the investor personally.
The cynic in me wonders if someone connected with Intel bought these shares just so the media would report that AMD are now also getting sued over this? Intel do seem rather keen to erroneously paint AMD as being in exactly the same boat as themselves with regard to the Meltdown and Spectre bugs and potentially considerable performance issues involved in fixing them. An anti-AMD PR attempt by Intel is the only thing that appears to make any sense.