I've been unable to reproduce this problem. Looking at the code, it seems that when the feature limit is set to 1, it is automatically overridden with a value of 64; I can see how this might confuse you.

If you can provide some steps to reproduce the issue, I'll look into this further.

Presumably this complaint could also be an interpretation of the fact that the regionating index is cached between requests, even if the per-tile feature limit changes. I've added code that clears out the cache when the regionating settings change, so this should be fixed as well.