Why do smart contract need to make any changes in for ERC-4337 to work?

Question

I was reading How to start with ERC-4337? and trying to understand why doesn't my existing smart contract needs to be changed in order to cater to ERC-4337.

Suppose we have an ERC-20 smart contract that assigns 1000 tokens to an EOA address 0x1000

and now that EOA 0x1000 choose to use the ERC-4337 to call transfer() to another EOA, will the ERC-20 smart contract sees the msg.sender() as 0x1000 still?

If the answer is yes, then how does ERC-4337 pass the msg.sender() to the ERC-20 smart contract?

If the answer is no, does this mean that EOA 0x1000 will need to transfer the ERC-20 tokens to the newly created AA first?

Answer 1

As it turns out, ERC-4337 requires you to migrate from an EOA to a smart contract wallet.

I was under the impression that an EOA automatically gains smart contract abilities.