ISO-Latin-1 has a code for English "æ" but not for French "œ".
A French colleague claimed that it was a dumb French representative to ISO who insisted that "œ" is not a linguistic significant letter but merely a typographical ligature for "oe", like "fi" for "fi".
My colleague said that, on the contrary, "œ" and "oe" sound differently. Wikipedia seems to agree.
He even showed two words that are distinguished only by "œ"/"oe" spelling. But I can't remember which. Does anyone know, please?