You're over-estimating the amount of heating/cooking involved. Ignore the article where he's doing everything all wrong, the plastics etc shouldn't be burning, only the solder is warming up and reflowing when done right. Fumes, if any would clear out anyways.
I agree that when done right (ie, following a proper SMD reflow temperature "curve"), all that should happen is the solder should flow and not much else.
Even so, just as I wouldn't reuse a pan or pot I had created sugar candy rocket fuel in to cook dinner (no matter how clean I tried to make it afterward), I also wouldn't reuse an oven for cooking purposes, that had been used for reflowing a PCB previously.
It just seems like a "best practice" to me to not reuse equipment in that manner for food cooking and consumption.
That's just me; I don't find the potential harm, no matter how objectively slight it might be, to be worth it in the long run.
