Re: How to understand these transactions all using the same address?
It seems you don't understand what dust is sir. Dust is an amount of bitcoin to small to be sent by your wallet. When you use several addresses, you get dust you can't send anymore. If you use one single address you won't get any dust.
You are wrong. As I said above, using a single address or using multiple addresses within the same wallet makes absolutely zero difference when talking about dust. If the input is too small to be sent, it will be too small to be sent regardless of what address it is on. Since UTXOs remain entirely separate until spent, it doesn't matter if all your dust outputs are contained within a single address - they are still dust.You are confusing addresses with outputs. Addresses can hold multiple outputs. Outputs are what are fed in to transactions. It is the value of the output, not the value of the address, which is important. An address with 5,000 outputs of 100 satoshi each will have a total value of 0.005 BTC, but the outputs are still dust.
I'm not wrong, and I'm not confusing anything. You are wrong.
Your wallet will not accept dust from other addresses, while it will take all utxos from your unique adress. That's why there isn't any dust when you use only one address.