Please read the whole of my post; I went on to say, "If you're lucky, your compiler and/or optimiser might be smart enough to spot what you're trying to do, and use the bit-addressing instructions."

Yes, Keil C51 can be smart enough to do this, but it is under no obligation to do so, and I wouldn't like to guarantee it - not even if the President said it would.
It could change between versions.

If single-bit operations are specifically required, then the compiler's single-bit extensions (if available) must be used.

"AND Nobody post that the SRC modifier allows the use of bit addressable instructions!"

Of course it does - cos it lets you use Assembler!! ;-)