Same way Ikora was able to yeet a nova bomb and then immediately use a chaos reach. Lore wise subclasses aren't really cut and dry. Osiris was able to quickly swap and activate all three types of warlock super (nova bomb, storm trance and dawnblade) in very quick succession. Technically our Guardain can do the same (use all supers at once) but gameplay reasons we are limited to only one at a time. Also class specific abilities gameplay wise are not the same lore wise. Felwinter is a great example of this. They are (as far as we know) the only warlock to ever perform a shoulder charge, thanks to Jolder teaching him how. If memory servers Felwinter activated blink and then as they exited blink went straight into a shoulder charge. Savathûn was able to wield any super she wanted at any time because there is no true "class system" for the Hive and she was the first Risen Hive. Plus game play reasons.