A polished result can still contain careless foundations.

A smooth surface tells you about the finishing, not the structure. Presentation is the last and most visible layer, so it is what gets attention, and it can be excellent while the reasoning, the data, or the joinery beneath it is shaky. The polish can even make people less likely to look, because it signals that someone was being careful.

When you are evaluating something impressive, deliberately look past the finish to one underlying claim and test it. And when producing your own work, resist the pull of spending the last hours on presentation while a known weakness sits underneath untouched.