I would like to know if training with a laundry punching bag such as this is equivalent to using a real punching bag?
It's hard to tell without examining or testing the actual item, but I'm skeptical that they would be the same.
- It's marketed as a "novelty", which is often used as shorthand for "not intended for regular use", and which suggests that the straps and sides of the bag probably aren't engineered to actually hold the weight of a properly loaded bag and/or handle the forces of the punch.
- The weight of dry laundry is likely not enough to create enough resistance for most training. And if the laundry is wet, it's going to create additional strain on the bag's straps.
Overall, I think this is meant to be a hanging laundry bag that resembles a punching bag, not something meant to be used as a punching bag, and it will likely break quickly if used as one.
It's definitely not the same. But that doesn't mean it's bad.
Many punching bags are much too soft or hard for certain types of training. Similarly, many are too light or heavy.
If you are training to box, you need to match your bag to the weight class of your opponents. During training, you can use bags of different weights, densities, and styles to help develop different skills. For example, uppercut training bags are very different from speed bags.
If you are just starting, the most important bag to have is one that you will actually use and one that won't cause injury. Many years ago, I learned that lesson the hard way which resulted in me being in a cast with a bone fracture for weeks.
That said, if you are strong, or use it a lot, I doubt the particular bag you found will last very long as a punching bag. The seams or material may likely tear very soon.
Whenever hitting any bag, make sure you properly protect your wrists, knuckles, and fingers. Wraps are mandatory if you want to reduce the chance of broken bones.
I think it depends on what you expect to train. If you want to train impact, you need something firm and heavy.
If you just need a surface with a little resistance and some heft to practice learning what it feels like to make impact, it doesn't matter.
What matters about any tool, in any craft or discipline, is what results you expect it to produce.