Notice how the ad doesn't mention the Tijuana Brass (except on the album cover image). They were positioning Herb more as a solo performer and a singer, especially considering there were 3 vocal tracks on the album that were all released as singles.
I think I've mentioned it somewhere on here in 20+ years, but I always thought of WARM as a sort of Herb solo album---only his photo on the front and back covers and for that matter the poster offer on the inner sleeve, as well as several tracks where it's clearly just Herb and some studio session players.
They needed to keep the TJB name alive---there was still a TV special on the books ("The Brass Are Comin''), so it's "...and the Tijuana Brass" on the cover and label---but