I mean, while I enjoy this idea as much as anyone, I don't think it's possible. If you tell HMRC that you don't have a British tax residency, then they will insist(very persistently) that you tell them which tax residency you do actually have, and with EU countries they absolutely do exchange information on taxpayers. It might take a few months or even years but they absolutely will catch up with you eventually.
Let’s say I move to Spain and start a business there cash-in-hand. I declare to HMRC that I earn nothing and I reside in UK. I proceed to collect UK subsidies, discounts on council tax, and various other benefits. I might rent out my house as well, either legally or illegally. Would I pop up on any radar? Unlikely. HMRC has no visibility of Spanish transactions and I don’t appear in any UK transaction, as far as they know I’m just a bum. If pressed by Spanish authorities (big if) I can just say I pay taxes in UK - which is “true”. If business in Spain does well enough I might just stop taking UK subsidies, to avoid scrutiny even more. If I never had to file self-assessment before I shipped out, I’m basically off the radar.
So, if you haven't decided that you'll stay permanently in the new country, but maybe instead you'll move to a 2nd new country, a 3rd and so on, then you might consider yourself an expat, but not an immigrant. At least that's how foreign students here, seem to refer to themselves: They're here for a few years, and then will probably leave, and they call themselves "expats".
And also, what about this: If you still have your identity in your home country (e.g. the culture there?), you'd think of yourself as someone from that country: "I expatriated from Home-Country". But if your identity is in the new country, then you'd think of yourself primarily as an immigrant to country New-Country?
I know that expatriate can colloquially mean a person temporarily abroad, but in this context, it refers to immigrants to Spain who generally intended to stay permanently.
I'm Irish, but once was an immigrant/expat in the US (in that I intended to stay permanently and to become a citizen, but things ended up not working out that way). I always thought of myself as an immigrant, but there were a lot of people I met who called themselves expats and never immigrants. Some almost seemed offended by the word. I think your comment about exceptionalism probably captured the reason why.
Some of them said that they did apply for that residency but were denied. Wonder why?
The group of people in the article either: have chosen not to apply for residency in Spain (noting that the technical deadline to apply is not until July 2021); were not resident in Spain before February 2020; and/or were not meeting EU rules for residency in Spain anyway.
Edit: I went reading. If you didn't get a padron (local residency certificate for your municipality) and hadn't formalised your status before brexit, (which, if you were working cash in hand is very likely), you would be behind a wall of prove-it processes which are based in paperwork, in Spanish. Where's your spanish drivers licence. Where's your tax file number. Where's your pre brexit registration. Prove you've been here.
Various expat assistance agencies have spent months offering people $ services to help them get through, including handy advice like be polite and dress smart and don't shout at the officials..
The overwhelming majority of longterm residents will have gone through the steps. The newspaper story is about the people who were never going to get over the line I suspect.
My language test theory has little to do with it.
Worth noting that local registration (padrón) is a requirement in Spain for all residents, including EU resident citizens, and also that there was 11+ months notice before this agreement came into force (if you don't want to count the 4.5 years notice since the referendum).
Meaning, people who were present in Spain but not legally resident could have chosen to "move" from the UK to Spain at any point until Dec 31, 2020, just by registering at the town hall like they were supposed to all along.
Your description of heavy paperwork seems to be a highly exceptional case which allows people who didn't register (but can prove they were resident) to now appeal.
But yea, loads of uk expats in Spain (who demographically trend over-50s) specifically voted for Leave while thinking nothing would really change for them. The exceptionalist mindset spread by UK tabloid media is incredible. Now they’ve lost their little tax-free paradise in the sun, and they’re back with us under they grey Albion skies. As an EU expat in UK, I will make sure to play the tiniest violin for them every day.