It was probably me.
I linked a study that examined it and found it to be a work of pure fiction:
The account of the wars of King ʿAmda Ṣeyon against the Islamic sultanates, an epic fiction of the 15th century
	
	
		
			
				
			
			
				
				Tous les commencements sont difficiles.Chaïm Potok, Au Commencement, 1976 [2019]. Le récit des guerres menées par le roi ʿAmda Ṣeyon contre les souverains de l’Ifāt et, plus globalement, contre les...
				
					
						
							 
						
					
					journals.openedition.org
				
 
			 
		 
	 
Not only were the sultanates independent, sophisticated and were in actuality rival kingdoms especially Awfat and Awdal that had the military and economic upperhand over them , not tributary rebel provinces in the way they are depicted.
The text also fabricates stuff like it claims that ʿAmda Ṣeyon appointed sultans (e.g., replacing Ṣabr al-Dīn with Ǧamāl al-Dīn) contradicts Walasmaʿ genealogies, which show smooth successions. Uninterrupted, with no puppet ruler imposed from the outside.
It gets the chronology of succession between the sultans wrong as well from what we know through local and external arabic sources that documents the walashma genealogy and it makes no sense at all.  It also lumps older sultans with newer ones like they existed in the same time frame. (e.g., Ḥaqq al-Dīn II [14th c.] with Ǧamāl al-Dīn [15th c.]) into a single conflict.
But yeah the whole thing is nonsense , imagine seriously entertaining the idea this mythical "Amda Seyon" 
single-handedly crushed all Muslim sultanates in one year (1332/3). No archaeological or Muslim sources confirm this. Awfāt and Awdal remained powerful for centuries after.
The text also includes mythic propaganda themes  and literary tropes like angels helped him fight and the Qadi Salih (The sorcerer judge). It reads like some medieval fantasy epic fantasy work.   Amda Seyon is imagined as the Heroic King, invincible warrior the ideal and Sabr Ad din in the story is the anthesis the cowardly traitor lmaoo. The narrative includes exaggerated battles, lists of territories, and eschatological themes, emphasizing a clash between Christianity and Islam.
But safe to say that the vassalage narrative is pure Christian propaganda, you can also see how this could be false in Muslim sources. The Walashma sultans defeated Ethiopian's armies multiple times often with much smaller armies. They had economic independence: Awfāt controlled trade routes to Zeila, taxing caravans, not the reverse. Diplomatic prestige: Sultans exchanged ambassadors with the Mamlūks (per al-Maqrīzī), something vassals couldn’t do.
After Saʿd al-Dīn’s death (1415), his sons built Awdal into a stronger power hardly behavior of crushed vassals. Sa'd a Din himself had vast military victories against them and was seen as the sovereign of Al-Habash(The Horn of Africa) in Cairo. He became legendary and famed in the entire Muslim world.
You can also tell from muslim sources and descriptions that the early Awfat rulers originated from Awdal launched military campaigns to conquere the Showa plateu and then built miltary garrison towns that act as buffer frontiers that seperates the Christian highlands from the Muslim Lowlands. So most of the battles that took place were border skirmishes and small scales raids.
On the Ethiopian side the short unsuccessful raids was pure gaajo(hunger) tactics as 
@novanova pointed out. They want the wealth and riches that the Muslims had and as they were living under starvation and feudal opression.