Hi Rob
I know where you're coming from but this time we have by far the best background signals of the winter, with a high amplitude phase 7-8 MJO propagation coupled with the polar vortex stretching and splitting being about as good as it gets (if only the timing was so optimal!).
I have spent some time trying to figure out what's messing with ECM's reading of the signals and whether it could be a genuine phenomenon that should be factored in, but so far have come up with nothing of value.
Anyway - as far as we (professionals in general) know, high latitude blocking is currently more plausible than not for mid-late Feb. That's as far as I can say without getting told off 
Model output, not just the ECM, no doubt, will have been adjusted, with the outcomes of the forecasts of the last 25 years. But several posters, have likened current outputs to those of the 60's and 80's. which suggests and you recognise, that we are perhaps missing the input of a factor, which has been absent or reduced recently. It is perhaps now returning?
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Dave,Derby