Index signature support was never added to the rule.

Even without adding an option to support position of index signature, the rule should be corrected to, at least, ignore index signature when checking order. The tslint replaced rule was not failing in this situation.

The tslint replaced rule was not failing in this situation.

We don't aim for 1:1 replacements with tslint when adding a rule. TSLint rules in many cases have options added that aren't used, or have options that should be on by default, etc.
When adding a rule that is analogous to one in TSLint, it's built for the use case.

The rule was built by a community member (as has been pretty much every rule).
At the time, they didn't have a use case for sorting index signatures, so they didn't add it.
None of the reviewers had an active use case for it either, so it was merged without it.

Either nobody has had a use case for this since the rule was implemented, or users have worked around it.

Happy to accept a PR to add support, if this functionality is important to you.

I'll try to see if I have time to create a PR. Unfortunately, I'm not sure I'll have time.

Just to be clear again: I'm not expecting the rule to allow to sort the index signature, but to at least ignore it.

EDIT: I take it, I'll try to add the signature to the list of items to order.

fixed in #1190