1.) The specific maze style used, with the semi-random angled lines within a circle shape, isn't the most mathematically simple form of a maze. If it was a grid pattern in a rectangle, there might be a tiny chance of two people making the same maze, but to create a maze of that style would require more creative programming, with more tune-able parameters, and more decisions left to the implementer.
2.) In order to choose from the vast number of possible mazes that fit a certain pattern, the algorithm is almost certainly going use some random number generation. Even if two people were using the exact same maze algorithm, they would have to also have to use the same randomization process, and start with the same seed in order to arrive at the same maze. I guess it wouldn't be impossible for both people to explicitly choose the same initial seed, (or arrive at it randomly) but that would be very unlikely.
Having the maze verts in the same positions is possible and not too unlikely. Having the same walls is astronomically unlikely. Even if you had exactly the same algorithm (possible, but unlikely) and the implementations used the random values in exactly the same order, you'd also need exactly the same random seed. There are a lot of possibilities for that seed.
I've seen a lot of code that either forgot to srand(), or misused it in some way so the output was pretty determinate. There are also a limited number of PRNGs in use, and they're most definitely not understood well by the majority of programmers; the crypto community knows this quite well. A collision may not be so unlikely after all.
(Try Googling "41, 18467, 6334" for example. "41184676334" also brings up some interesting results.)
For example, here is some code I wrote to test my own prng:
srand(1000000); for( int i = 0; i < 10; i++ ) printf( "%d\n", rand() );
printf("====\n");
srand(1000001); for( int i = 0; i < 10; i++ ) printf( "%d\n", rand() );
And here is the result:
21585 18586 29373 4301 3304 21158 23657 21142 2144 26110 ==== 21589 29335 14469 28364 13618 25085 26770 18215 18656 19962
As you can see, they diverge really quickly.
