It would be more correct to say that EJs and IPs are preferentially closed-loop thinkers.
THe filter thing... for IPs and EJs every function works as the mirror opposite of how it works for the other so lumping these temperaments together is usually a mistake. Great care should be taken when discussing them as a combination.
As for focus, it all depends on how you define focus. Focus is a necessity for productiveness and if we take that into consideration it seems like Ejs are more focused than Ips. But it's all how you define it.
Here's a description by a Fi type about how they experienced their Ej friends' extrovert function:
Terry looked at me. He said: “Do not underestimate this anger. This anger was the engine that powered Good Omens.” I thought of the driven way that Terry wrote, and of the way that he drove the rest of us with him, and I knew that he was right.
There is a fury to Terry Pratchett’s writing: it’s the fury that was the engine that powered Discworld. It’s also the anger at the headmaster who would decide that six-year-old Terry Pratchett would never be smart enough for the 11-plus; anger at pompous critics, and at those who think serious is the opposite of funny; anger at his early American publishers who could not bring his books out successfully.
The anger is always there, an engine that drives. By the time Terry learned he had a rare, early onset form of Alzheimer’s, the targets of his fury changed: he was angry with his brain and his genetics and, more than these, furious at a country that would not permit him (or others in a similarly intolerable situation) to choose the manner and the time of their passing.
And that anger, it seems to me, is about Terry’s underlying sense of what is fair and what is not. It is that sense of fairness that underlies Terry’s work and his writing, and it’s what drove him from school to journalism to the press office of the SouthWestern Electricity Board to the position of being one of the best-loved and bestselling writers in the world.
It’s the same sense of fairness that means that, sometimes in the cracks, while writing about other things, he takes time to punctiliously acknowledge his influences – Alan Coren, for example, who pioneered so many of the techniques of short humour that Terry and I have filched over the years; or the glorious, overstuffed, heady thing that is Brewer’s Dictionary of Phrase and Fable and its compiler, the Rev E Cobham Brewer, that most serendipitious of authors. Terry once wrote an introduction to Brewer’s and it made me smile – we would call each other up in delight whenever we discovered a book by Brewer we had not seen before (“’Ere!’ Have you already got a copy of Brewer’s A Dictionary of Miracles: Imitative, Realistic and Dogmatic?”)
Terry’s authorial voice is always Terry’s: genial, informed, sensible, drily amused. I suppose that, if you look quickly and are not paying attention, you might, perhaps, mistake it for jolly. But beneath any jollity there is a foundation of fury. Terry Pratchett is not one to go gentle into any night, good or otherwise.
He will rage, as he leaves, against so many things: stupidity, injustice, human foolishness and shortsightedness, not just the dying of the light. And, hand in hand with the anger, like an angel and a demon walking into the sunset, there is love: for human beings, in all our fallibility; for treasured objects; for stories; and ultimately and in all things, love for human dignity.
Or to put it another way, anger is the engine that drives him, but it is the greatness of spirit that deploys that anger on the side of the angels, or better yet for all of us, the orangutans.
Terry Pratchett is not a jolly old elf at all. Not even close. He’s so much more than that. As Terry walks into the darkness much too soon, I find myself raging too: at the injustice that deprives us of – what? Another 20 or 30 books? Another shelf-full of ideas and glorious phrases and old friends and new, of stories in which people do what they really do best, which is use their heads to get themselves out of the trouble they got into by not thinking? Another book or two of journalism and agitprop? But truly, the loss of these things does not anger me as it should. It saddens me, but I, who have seen some of them being built close-up, understand that any Terry Pratchett book is a small miracle, and we already have more than might be reasonable, and it does not behoove any of us to be greedy.