Skepticism aside, what did they do and what did they find? They stimulated left or right premotor cortex while subjects made lexical decisions to manual (e.g., throw) or nonmanual (e.g., earn) verbs. Left but not right PM stimulation lead to faster RTs to manual verbs compared to nonmanual verbs.
This effect challenges the skeptical view that premotor activation during linguistic comprehension is epiphenomenal... These data demonstrate a functional role for premotor cortex in language understanding.
I think they've shown clearly that premotor cortex plays a role in lexical decision. The source of this effect remains unclear (does it affect the semantic representation or just bias, e.g., prime, the response) and more importantly, the relation between lexical decision (the measured behavior) and language understanding (the target behavior) is far from clear.
In short, they have done nothing to curb the skepticism regarding the role of premotor cortex in language understanding.