There are people who care about L1TF mitigations. I am not going to question their motivation. In any case a hint how to make the mitigation active again sounds more useful than something that sounds as scary as "you are vulnerable".
FWIW an early version of these patches automatically limited the available memory, but Linus pointed out that people likely prefer their memory. I still think his reasoning was right, and likely applies to your message too.
-Andi