Rule 7.0.5, example non-compliant with 7.0.6?

[cgpzs]

Rule 7.0.5 presents this example:

Code:

u8a += static_cast< uint32_t >( u8b ) // Compliant - u8a -> unsigned int

Yes, compliant with 7.0.5. But this code then violates 7.0.6, since there is an implicit narrowing conversion from uint32_t to uint8_t in the assignment, right?

Code:

u8a = (uint32_t)(u8a) + (uint32_t)(u8b);

So, how are we supposed to write this type of code? Like this?

Code:

u8a = static_cast<std::uint8_t>(static_cast<std::uint32_t>(u8a) + static_cast<std::uint32_t>(u8b));

Does that really make the code safer?