Why does the bar say shipping is free before my threshold?

Because checkout already charges nothing for that cart's delivery. If everything in the cart is in a shipping class whose Flat rate is 0, or a shipping plugin gives the cart a free rate of its own, the bar says "You have unlocked free shipping." with a full track rather than asking the shopper to spend more for something they already have. It reads the rates WooCommerce worked out for the cart, the same ones checkout shows, and local pickup never counts.

To hide the bar in those carts instead, choose Hide the bar under Setup → Free Shipping Goal → When delivery is already free another way. If a shipping plugin shows 0 when its price is not known yet, a developer can leave it out with the trfs_free_rate filter.