That's hypothetically correct for most recipes, but practicality is a key factor in those guidelines for home canned foods: how long will the seals of the lid last? How much would an average person disturb the cans to risk cracking the seal? How imperfect is the average home canning job? How imperfect is the average recipe?

"Forever" is correct if this were a perfect recipe, perfectly canned in a space-aged orb, in a laboratory.

But it's important to also consider expiration dates as meaning "how long can I, as an average, imperfect person, expect this to last based on how many tiny mistakes I'll make in practice as well as the life of the materials I used."