Can silk stop the raging Orc? or rather do fragile structures provide less cover?

The Player’s Handbook (pg. 196) reads

Walls, trees, creatures, and other obstacles can provide cover during combat, making a target more difficult to harm.

However it only defines degrees of cover (1/2, 3/4, Full) in terms of area covered. RAW it then seems that a curtain of silk provides as much cover cover against the attacks of a battle axe wielding Orc as a stone wall. Reasonably, however, it would make more sense just to confer the benefits of Unseen rather than the benefits of cover.

Rules as Written is there something I am overlooking and if not what is there a more reasonable system of adjudicating cover?