In this case, they didn't copy the software. They rewrote it from the ground up with different tools. They did copy almost 100% the look and feel. But that is not 100% of the "product"...far from it.
How closely to a pre-existing design or market space does a product need to be before it offends you? Do you have a methodology to measure this?
How much time have you spent trying to woo venture capital? In my experience, one of the first questions I get hit with is "is there anyone else doing something similar?" If the answer is no, this is a red flag.
A typical and expected elevator pitch is "its like X but for Y". Hybridization is the game here. It is common and quite acceptable to say "its like X but for China".
The creator of this new product did change something...something critical... "its like StackOverflow but for China".
"Derivative", not clone.