John M. Manly presents a theory, which I will outline below, that Chaucer’s Reeve was based on a real person. If you find this theory plausible, then the explanation for the detailed description of his hairstyle is that, as with other details given about the Reeve, Chaucer intended to make the identification clear to his readers.
Three features of this description first suggested that Chaucer had in mind a definite person. One was the statement that the Reeve came from Norfolk, beside a town called Baldeswelle; the second was the description of his house as situated on a heath and well shaded by green trees; the third was the specific statement that he had had charge of the manor since his lord was twenty years of age. The last two sounded like bits of personal observation by Chaucer, the first suggested the question why Baldeswelle—an insignificant village, far from London, almost in the “ferthest end of Norfolk”—should be mentioned, unless Chaucer had some particular reason for interest in it.
John M. Manly (1959). Some New Light on Chaucer, p. 85. Gloucester, Mass.: Peter Smith.
Manly tells us that estates at Baldeswelle (modern Bawdeswell) belonged to the earls of Pembroke in the 14th century, and in particular to John Hastings, 2nd Earl of Pembroke. Born in 1347, John inherited his father’s earldom and estates in 1368, aged twenty, but soon departed for Aquitaine to fight in the Hundred Years’ War, leaving his estates to be managed by deputies. This matches the situation in Chaucer:
His lordes sheep, his neet, his dayerye,
His swyn, his hors, his stoor, and his pultrye,
Was hoolly in this Reves governynge,
And by his covenant yaf the rekenynge,
Syn that his lord was twenty yeer of age
When Pembroke died in 1375, his heir was just three years old, and his estates were granted to custodians until he should reach his majority. The Norfolk estates were assigned to the custody of his grandmother, Margaret, Duchess of Norfolk, and
on March 9, 1378, King Richard granted the custody of the estates in Wales to Sir William de Beauchamp.† In this last transaction the mainpernors or sureties for Sir William de Beauchamp were two: John de Beverle and Geoffrey Chaucer of London.
Manly, p. 89.
† The young earl’s cousin, once removed.
Manly suggests that Chaucer’s connection with the custody of some of the Pembroke lands makes it plausible that he would be aware of the situation at Baldeswelle too. For some at least of the estates did not fare well under custody:
Sir William de Beauchamp was much engaged in the king’s business in Scotland and France and from 1384 to 1392 was captain of Calais. He could hardly have given much personal attention to the lordships and lands committed to him. In the autumn of 1386 investigation of his management was officially begun and in 1387 (February 22 and October 6) an arrangement was made between Sir William de Beauchamp on the one side and the young earl’s grandmother on the other (his mother having died in 1384). It was agreed that Sir William should be relieved of the custody of the lands.
Manly, p. 91.
So it is plausible that there was mismanagement at Baldeswelle too, along the lines described by Chaucer:
Ful riche he was astored pryvely:
His lord wel koude he plesen subtilly,
To yeve and lene hym of his owene good,
And have a thank, and yet a cote and hood.