This is someone who like three years ago said in an interview that he preferred training over racing.
His real top quality is endurance. He is strong in all kinds of terrain especially uphill, reads races well etc but endurance is key. The stage win in Tirreno-Adriatico last year, Liége, the results in Strade Bianche and Amstel, the stage in Tour de Pologne last week, Lombardia; all turned out as real difficult races because racing started early, weather, really hard courses, Evenepoel, strong teams racing hard. I think maybe the moment he realized he could profit by also making races harder in person was two years ago where he attacked with Valverde far from the finish whenever possible in the Spanish races.
It's ten years ago Fuglsang was fourth in Lombardia, second in Emilia and fourth in Amstel. In the stage races he was very good from day one; third and fourth in Tour de Suisse, sixth in Catalonia and Dauphine and dominting gc wins in Slovenia and Austria. These qualities of being versatile and with great resistance in long races has always been there. Note also the best performance in the TDF 2013 was the Alpe d'Huez x two stage, probably the toughest stage, where he was fourth of the top ten riders. But still it was a mistake to target TDF so much, as many people has said for years. Because (a) he has not been able to handle Team SKY style accelerations at the end of mountain stages and (b) crashes (2014, 2017, 2019) and a predetermined role as strictly support (2015, 2016) means the only real unhindered race was the super average 2018 and (c) all the other races was secondary and he always only hit peak level condition in June.
Before last season the story was focus had been on short maximum efforts, three to five minutes, with the idea to better follow attacks late in mountain stages. But presumably it made him improve in the one day races instead. Plus he is skinnier than before, used to have real chunky arms.
My take: Fuglsang is a cyclist that has evolved and improved, a little similar to Mollema maybe, but not to a crazy exaggerated weird new level.