Okay, GPT4 said there a just 189 non-overlapping 50km bands (horizontal, vertical, and diagnoal) in Europe and then continued to calculate the chance to land those 7 points in any of the 189 bands and gave a result in the order of 10^-12.
Also, the probability of the first 2 points will always be 100% because they define the line.
Also, it's not 7 random points, it's 7 of thousands of random points.
Ah - I missed this one.
I think if you set the probability of the first one at 1, then the rest works perfectly at any angle of band. I could be wrong, but intuitively that seems correct.