Answer
No, the bubbles in the solar heat sheet cannot direct more solar energy into the swimming pool. To say that the "lenses" in the sheet focus additional solar energy into the water is a marketing gimmick.
Work Step by Step
The solar heat sheet is just as large as the swimming pool's surface, so it can’t collect any more solar energy than that which was going to enter the pool anyway.
A magnifying glass can collect light energy and concentrate it at its focal point, setting paper on fire, for example. The key point is that the diameter of the lens is much larger than the area upon which the light is focused - and that is not the case here.
The sheet will keep the pool warmer by preventing evaporation, and the presence of the insulating air bubbles make it more effective than a thin sheet of plastic of the same weight. So it's better than nothing.
