All buck drivers have loss's, usually 10%-25%, as noted here: https://budgetlightforum.com/t/-/28594 in the OP, post #2 here: https://budgetlightforum.com/t/-/31322. Reducing loss's usually means increased cost in parts and complexity. Dunno what the Texas Buck driver does, but it's got loss's, just how much is the question. Voltage conversion never comes free.
Refer to Wikipedia article here as well, them mention loss's and efficiency: https://en.wikipedia.org/wiki/Buck_converter
I've never seen anything posted to say otherwise, that buck drivers always have loss's.