It is sincere from the standpoint of honesty, at least they do not pretend to want to spend time with you. When they rebuff your invitation, at least you know that they are candid and forthright.
I may wonder why they will always reject me; I may question myself “What did I do to cause this?” No communication will ever come, this fact is well established and does not regain consideration.
Still, I cannot stop feeling disappointed. I love this person; I want this person to love me. The fact that my love is not reciprocated, in no way changes how much I love.
I am stuck here with love disappointment. At least, it is genuine love and genuine disappointment.