Why contracts-upgradeable has IERC721Upgradeable (and I<whatever>Upgradeable)

:1234: Code to reproduce

interface IMyContract is IERC721 {
...
}

contract MyContract is IMyContract, ERC721Upgradeable {
...
}

Then when I compile I get errors like these

11 | contract PolicyNFT is IERC721,
   | ^ (Relevant source part starts here and spans across multiple lines).
Note: Definition in "ERC721Upgradeable": 
   --> @openzeppelin/contracts-upgradeable/token/ERC721/ERC721Upgradeable.sol:184:5:
    |
184 |     function safeTransferFrom(
    |     ^ (Relevant source part starts here and spans across multiple lines).
Note: Definition in "IERC721": 
   --> @openzeppelin/contracts/token/ERC721/IERC721.sol:136:5:
    |
136 |     function safeTransferFrom(
    |     ^ (Relevant source part starts here and spans across multiple lines).

TypeError: Derived contract must override function "safeTransferFrom". Two or more base classes define function with same name and parameter types.

I think XXXUpgradeable contracts shouldn't define new interfaces but instead implement the standard ones. Interfaces are the same between upgradeable and non-upgradeable contracts.

:computer: Environment

    "@openzeppelin/contracts": "^4.2.0",
    "@openzeppelin/contracts-upgradeable": "^4.2.0"

q