It then proceeds to show a map depicting he walked from Texas, Not Florida (AT MINIMUM a 374 mile difference), westward.

Ah, yeah, that is what I remember from hearing this story many times growing up. Galveston to Mexico/New Spain after a decent amount of time spent on Galveston itself. Was wondering where the hell the Florida thing came from.

Edit: I think they are counting the time on the ship, they went past Florida hugging the coast before being shipwrecked.

https://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Expedition_Cabeza_de_Vaca_Karte.png/1920px-Expedition_Cabeza_de_Vaca_Karte.png