Depends on the pot & the plant. A lot of the cheaper aquarium plants will do just fine in aquarium gravel. <Some, like anubias or java ferns, don't need any substrate at all & can be tied to a rock or driftwood, etc.>
It is fairly common to have potted plants in goldies tanks to prevent the fish from digging up the plants. To have really good plants, you want to use a good size pot (like 3") - an unglazed terra-cotta pot works well - so the plants have room to grow. I wouldn't leave the plants in those tiny plastic pots, even with slots. 1. The slots are too small for roots to grow out of. 2. The plants are usually packed in rock wool & such, not ideal planting medium. 3. Even if the pot & medium is ideal for the plants, once the roots grows out of the pot into the gravel, it is no different than if you had planted the plants in the gravel directly. If the plants actually needed good substrate, you will need to have all the roots in the substrate - ie a big enough pot to hold all the roots.
Your best bet is to ID your plants to see if they actually need a fancy substrate. Most plants in the typical lfs don't.
