No, but Google pulled it for a while which must have had an effect on roll-outs. FWIW, our N5, N5X, and 6P just received updates this week and none had received the March 18 security fix. We usually get them mid-month.
I just rec'd the update to 6.0.1 on my N9 LTE (last Wednesday). Maybe they were focusing on that. Hopefully this means that the security update will come soon.