When I got to the airport, I thought I'd ask about getting the fee waived anyway. I explained my situation and showed them my Delta itinerary that lists my status as "Flying Blue Platinum Medallion / Elite Plus" (sic). Ground staff conferred for a minute then decided they could do it. By their own admission, they don't get many Skyteam elites on Delta codeshares, so I am guessing that I lucked out, with a combination of helpful, friendly staff, an unusual situation for them and some ambiguous wording on my paperwork!