@Ray ****
I believe it started sometime in early January, when the Embassys started to require the insurance.
IMO, at some stage, the insurance will be required in order to get the extension the same as it's required for an extension based on an O-A visa.
Right now, it isn't yet required for an extension based on a Non O.
Lets not forget, you need the insurance for gaining AND extending the STV visa as well.