Thanks for suggestions, Air France shows my reservation as morning departure on A350 as I expected.

it's a good point not to trust Delta in partner flights, but I book ticket through Delta, so I expect Delta to sell me ticket as advertised. Delta also tells me about schedule change and asks to accept or reject, which I have to do through Delta. What if Delta says there was schedule change when there was none (because it happened before I purchased ticket)? Then I call Delta and they are completely clueless about flight departure time.

I think there is just some bug, which was triggered by the schedule change few weeks ago. And it's a new bug, because I had hundreds of partner flight changes without any issues on DL side. The bug can be reproduced today by booking this specific flight => you get schedule change notification right away and all weirdness. I gave repro steps to agent, but I doubt agent reported it to proper department.