That 14th century passage of Richard eating Saracens is fictitious, for reasons @T.E.D. has gone into. Richard Coer de Lyon is a romance, not history. In this story, King Richard first became a cannibal when he requested pork to cure himself of a malady, and was given a Saracen instead - as a practical joke by his knights.
Richard Coer de Lyon is a spectacular story of cannibalism performed by the king of England, Richard I ... Richard's illness is historically documented, but what follows as cure in RCL is purest romance ... At the knight's detailed instructions and unbeknownst to Richard, the steward has a young, fat Saracen killed, opened up, and flayed; boiled with saffron and other spices, the freshly killed corpse is turned into a broth for the king's delectation ... Richard's folk are delighted at their kindly, healthful, and private joke at the king's expense - "His people turned themselves away and laugh" - a collective prank ...
What is extraordinary about this bizarre performance of cannibalism by a celebrated English king is less the cannibalism per se than the depiction of cannibalism as a joke in a popular romance.
- Heng, Geraldine. Empire of Magic: Medieval Romance and the Politics of Cultural Fantasy. Columbia University Press, 2003.
Apparently it is no more than a crude joke in a generally ahistorical piece of fiction.
The romance, unlike many accounted for in this project, roots itself distinctly in crusader history, recounting the campaigns of Richard and the armies of the Third Crusade. Nevertheless, the romance deliberately warps history in order to respond to current cultural concerns and investments.
- Norako, Leila K., "Richard Coer de Lion", The Crusades Project, University of Rochester.
The other example listed in the question, however, has a firmer basis. A historical case of cannibalism did occur during the First Crusade, at Ma‘arra in 1098. The incident was frequently attested to by contemporary writers, some of which identified the cannibals as "a group of pilgrims called the Tafurs".
Almost all the dozen chroniclers who wrote books about the Crusade in the twenty years following Jerusalem’s capture acknowledge it, sometimes with disbelief or disgust or denial, but always with discomfort. The broad details of the story are clear ... on January 13, 1099, under intense pressure from his followers, Raymond gathered his forces and continued the march to Jerusalem. At some point during this activity - as we shall see, the sources diverge significantly - an indeterminate number of soldiers ate from the flesh of enemy dead.
- Rubenstein, Jay. "Cannibals and Crusaders." French Historical Studies 31.4 (2008): 525-552.