Nonsense. Rest is referred to as salvation in the context of Heb 4. And when Jesus was stating this in Matt 11: 20 he was talking publicly where everyone could hear him.
Then Jesus began to denounce the towns in which most of his miracles had been performed, because they did not repent. Matt 11:20
In the same declaration he announces still out to them all,
Come unto me, all ye that labor and are heavy laden, and I will give you rest. Take my yoke upon you and learn of me; for I am meek and lowly in heart and ye shall find rest unto you souls. Matt 11:28
How exactly could that not be said to be offering all grace?