In FastBloom(Bloom Optimized) shader, what's the difference between Standard and Sgx blur type?

When I use the FastBloom (Bloom Optimized) image effect, I noticed that there are two blur types, which are "standard" and "Sgx".

When I toggle between them, there is no difference on rendering side. Then I check the shader, both of them are 7 * 7 gaussian blur. The way they do the for loop is different, but they all have 7 times texture reading, so there shouldn't be dramatic performance difference.

So what's the difference? And why the second one is named "Sgx"? What does "Sgx" stand for?