tl.add() is the better option, the only thing I don't understand is why it jumps from the first tween in the timeline back to opacity 0.5.... when the flip animation is completed...
See the Pen poBjery?editors=1011 by destroy90210 (@destroy90210) on CodePen
Update: ok I think i got it, i need to add opacity: 1 also to the final state, because this would be used at the end as inlinestyles...
gsap.set(el_scalingTile, {
width: "100%",
height: "100vh",
top: 0,
left: 0,
position: "absolute",
opacity: 1 // <----
});