[ScrollTrigger]

Maybe something like this:
 

// Mark section as loading
let introLoading = true;
gsap.timeline({
    ease: "power2.out",
    scrollTrigger: {
        trigger: '#section-intro',
        pin: '.wrap',
        start: "top top",
        scrub: 0.25,
        snap: false,
        onEnter: self => {
            
            // Mark as loaded after first time enter event is fired
            // Would be same as on init
            if ( introLoading )
            {
                // Mark as init after 1000ms
                setTimeout( () => {
                    introLoading = false;
                }, 1000);
            }
        },
    }
});