This appears to happen due to argument positions, and the fact that tallyVotesForShouldUseDoubleFormat() doesn't set NotUsingDoubleFormat. A great example of this is the test case for https://bugs.webkit.org/show_bug.cgi?id=109491
Created attachment 232813 [details] test case
<rdar://116397731>
Fixed in https://github.com/WebKit/WebKit/commit/bf2f05e02c8a12f6b716ea8bc21e62852d8493ac.