When is a past tense not a past tense...?

An interesting comment I had into the site today concerned the final example on the site's page about how to say 'would' in French.

This last example deals with the (perhaps least common) case of 'would' in English being used as a historic future: "The king would die in 1457". The equivalent of this usage in French is generally to use the future tense: Le roi mourra.... Rather than being a misformed past historic (the PH of mourir would of course be mourut), this is a genuine future tense-- just with a past or future-in-the-past interpretation. If I had a euro for every time I'd seen phrases such as "The king will die in 1457" in French museums, I'd have enough money for at least one SNCF baguette.

Now, the comment received appeared to be assuming that I had mistakenly written mourra instead of mourut, whereas in fact I genuinely intended the future form. But this got me on to the question I wanted to pose to readers: is there any genuine source of confusion here? I thought it was clear enough, but do I need to add an extra note to highlight that this really isn't a future tense? Comments welcome!