Not true. In spanish, "ad" is usually anuncio, or sometimes comercial or publicidad. Propaganda can also be used, but is less common than those i think, I've never heard it used.

I once read an original edition of Bernays' Propaganda (1928) with its title in a jaunty typeface on the cover, before the word had a negative connotation.

Pic of its cover here: https://www.baumanrarebooks.com/rare-books/edward--bernays/p...

I have definitely heard "propaganda" in South American Spanish-speaking countries. Perhaps a regional quirk?

You can also use "publicidade" in Portuguese, but "propaganda" is not used exclusively for "political propaganda".