According to the LASS 3 articulations chart, it doesn’t have any cello (or bass) ensemble trills. The solo (First Chair) cello apparently has ’em though. I know LASS 2.5 doesn’t have any cello & bass trills at all, so if anything, the chart indicates that a solo cello trill was added in LASS 3.
I don’t have LASS 3 yet so I can’t comment authoritatively, but I know that some libraries use a unified UI switcher design for all patches, even if a particular articulation isn’t available for a particular instrument; you just can’t activate it. (For instance, in Cinematic Studio Brass, all patches have the “Muted” articulation tile, but some instruments like the Tuba can’t turn it on, so it’s permanently greyed out and nothing happens when you click it.)