I don't think so. This one seems to defy the rule.
"A his-toric day"
"An his-toric day"
Both seem to work correctly with American pronunciation.
Journalists and films seem to use "an historic" with an American accent, which breaks the rule but still feels correct.
For most words the indefinite article is clear. This one feels weird.
They do, but only because it's been adopted from British media and literature. You might even say it's a symptom of being over-read, if that's possible.
"An historic" is certainly used in the US, but it's wrong in all contexts.
> This one seems to defy the rule.
No it doesn't. If I pronounce the "h", then using "an" sounds weird. If I don't, then "a" sounds weird.
> Journalists and films seem to use "an historic" with an American accent
Curious if you have a link to a video of this, I can't imagine it sounding correct.