I'd say the proportion of "unlikely patterns" in a private key of size n is more like very close to 0.00% (zero percent) the higher n gets. And it goes towards 0 really fast as n grows exponentially.
You and I are probably talking about different things. I mean, it is extremely unlikely that among the remaining undisclosed keys there are patterns such as ffff or 8888 or more repetitions of the same digits.
At the same time, I doubt that such combinations as, for example, c5ec5e or dd4dd4, etc., can be considered unlikely. Therefore, I think it is possible to discard numbers containing patterns of more than three identical digits.
Without any calculations, I roughly assumed that there could not be more than 20% of such numbers in the range.