IMO Hajrudin reaching the point where he can fight Dorry and Brogy makes sense. Look at how far Koby came from Romance Dawn to Enies Lobby. Similarly, look at Romance Dawn Luffy to Marineford Luffy. Romance Dawn Luffy was getting pushed by Buggy, then heavily pushed by Arlong. Marineford Luffy was Vice Admiral level, with some Haki, but no consistent use of it, and strong use of his Fruit with Gear 2 and 3.
Mindset is what gives you the biggest gains in One Piece.
We've had a lot of time pass in universe since Dressrosa, Hajrudin being able to fight top tiers for a bit isn't wild. But, this is injured Harjudin, so, he'll be... idk, fairly effective, before getting knocked out.