The fact that theirs is a chaste love, "Difference of sex we never knew, / No more than guardian angels do," makes the poem an interesting testament of love. The fact that the imagery must hearken to their future embrace in the grave, disturbed by a grave digger, also makes it an interesting testament of love. Both of these are diametrically opposed to the expected nature of love poems.
In spite of the somewhat macabre image with which the poem begins, this poem is really a discussion about platonic love, as the speaker imagines his own body being dug up at some point in the futrue to make way for a new corpse. The gravedigger, finding a "relic" of golden hair wrapped around the corpse's forearm, will see this as a symbol of the love of the speaker for his mistress and leave them alone, according to the Renaissance belief that at Judgement Day their souls can be reunited because of the belief that souls would seek their body parts to be re-assembled for their new resurrection. Such a grim focus naturally leads itself to a very novel presentation of the theme of love.