Furniture are designed to be furniture. There's a reason why there are specialized makers for keyboard stands. Shoes are light, and shoe racks are meant for that kind of weight. Tthe shoe rack in the clip showed it taking in 49, 61 and 76 keys keyboards. Can't see what kinds of keyboards and hence don't know the weight. But I would be very careful.
Another point. Storage may be one thing. But playing them off the shoe rack is going to add additional stress on the rack. Hence, the shoe rack better be STRONG!