It's been quite a while since I last heard the early Beach Boys LP's in non-Monaural pressings tostado (I used to have them all), but I specifically remember being surprised by the true Stereo Surfer Girl album. Emblazened across the top of the LP jacket's front cover is the huge Capitol Records' <STEREO> banner, while the other BB albums that aren't Monaural are labeled Duophonic (sometimes in very small type ;-). I'm quite certain about Surfin' Safari, Surfin' U.S.A., Little Deuce Coupe, Shut Down Volume 2, All Summer Long, Smiley Smile (a really bad recording anyway, unfortunately. It contains some of my favorite Brian Wilson writing), and Wild Honey. The last two Capitol albums, Friends and 20/20, ARE regular stereo. Their next album---Sunflower, the first for Reprise Records, had a paragraph on the back of the gatefold cover, detailing how the recording was a "True Stereo" one, not a multiple-Mono one as I described earlier. Pretty Audiophilic! I don't know whether or not it's true, but who was talking about such things in 1970?!
By the way, Capitol Records released three Beach Boys albums in 1963, three in '64, three in '65, and two in '67, with "only" one (Pet Sounds) in '66. My how the record business has changed!