Yea I remember reading this advice too, might have been yourself commenting it...Back in 2016 when I was rebuilding after the Great Swirl Flap disaster, I asked Ned at Autolusso about oil feed to the turbo, since a lot of cars insist on new pipes.. My turbo had escaped damage, aside from a little interior rust (probably the previous owner, who'd occasionally run the car for a year while he pondered what to do) that caused the vanes to stick and overboost. Ned said 'get rid of the filter in the banjo bolt - they kill turbos'. But it's oil that's just passed through the paper filter anyhow, so can't do anything useful.
This filter is a tiny tube of very fine metal gauze with only a couple of very small feed holes to the turbo, and it eventually becomes blocked with sludge - and then the turbo bearings are destroyed through oil starvation. Sludge is of course a particular risk with a car that has neglected oil changes. Of course, if you just put it back with a good or new turbo, the oil feed may still be limited and the new turbo will be quickly murdered. So I drilled it out.
This seems to have been a Very Good Idea, since the turbo is still near silent and continues to works perfectly on my Stage 1 mapped car. Mind you, I use Fuchs Titan-S 10W40 estar oil, change the oil at 6k mls max (though longer time period than 1 year), allow oil to warm up through gentle use, and generally drive in a clutch/DMF preserving manner.
I've kept up with oil changes well ahead of schedule, every 6-8k miles for the 160k miles that I've been driving it for... Also had decent oil for all its life (Fuchs GT1 XTL 5W-40, or a similar full-syn offering from Gulf/Motul). Quietly confident that it's not sludge that's killed it, but we'll wait to see what Loz reports when they get their hands on it... But 194k miles isn't exactly a bad run for a factory turbo...
If it gets fixed I'll get a replacement banjo from AlfaWorkshop and drill out the gauze - not that I think I'll get another 194k miles out of the rest of the car!