You are guilty of nothing. The extropians list is far older than the
transhumanist list, and the two lists were started completely
independently of one another, so there are no rules at all about which
content is appropriate for which list.
Extropians are a kind of transhumanist, so anything of general
transhumanist interest would be of interest to both lists. You don't have
to feel obliged to subscribe to both lists just because you're interested
in reading one or the other of them.