Interesting development on my side.
Called the French AF PSL tonight using skype; got a friendly agent after 30 seconds or so waiting, explained my situation - and my worry. She spent about 45 min on the case, checking also with supervisor I suppose. She first confirmed that the ticket was still alive, booked in Business from ICN-CDG (AF metal) than CDG-AMS and AMS-BRU. I explained my issues on the way to HKG, but we quickly narrowed down this was not a compensation request as I did not have (yet) asked for it. There are very few details on this KLM refund request also on her side. Eventually she figured out that this refund request was regarding a downgrade (does not seem to be a ticket cancellation, but she was not 100% sure), although I confirmed to her that at the end, I was rebooked in J for the CDG-HKG segment, although on a different ticket number than the one mentioned on the refund request receipt. She could not tell the amount either, and told me she added notes on the file stating that I never requested a ticket refund and/or cancellation and recommended to monitor frequently my reservation and credit card statement. So let's wait and see I guess. I hope nobody will touch the ticket, right now my ICN-CDG sector is in Z (original class was O). When asked to receive the eticket receipt by email (for some reason KLM does not send it anymore for all bookings for a few years already, while AF still does that, only the travel memo was available to her (this is what you receive from KLM as booking confirmation). The reason I asked for it was to see the fare basis of the booking, but she could not retrieve that information on her system and I cannot see that either anymore on the manage my booking section of the website (usually, it is below the fare conditions for rebooking and refund etc...). Strange... But she anyway confirmed once again the booking was a legit business class booking. And the call was recorded on my side... just in case !

In the meantime I asked using the app a retrocredit of the CDG-HKG I was rebooked onto since the miles and XP had not posted (it's usually within 24 hours after departure for AF/KLM flights). Was surprised to receive way more miles than expected for this segment, about 12k+ (with 36XP as expected) while the entire trip was supposed to yield about 13k-ish miles. Not going to complain...

But the funnier story happened a couple hours later when I received a call from a Portuguese number. It was the customer service of AF calling me regarding the compliment email I sent to them yesterday about the good service received in CDG, explicitely naming the agent who helped me. The line was however very bad, so she indicted to me that she would contact me by email, which I received about 10 minutes later.
Again, the email sent yesterday was to compliment someone, this is the category I choose on the website. I started the email by stating that I would send my compensation and explanation request later regarding the downgrade situation and the terrible service in AMS, but that for now I wanted to praise the service received in CDG.
The return email received started my bringing the usual apologies for this situation adding that due to the delay, I was eligible to 600 Euros compensation per EC261/2004 which could be increased to 800 Euros if the future travel credit option was selected. She also added some apologies for the downgrade of the CDG-HKG sector, and indicated that 75% of the cost of the segment will be refunded to me, in addition to 44000 miles for the commercial compensation (not a typo - fourty four thousand miles). I certainly mentioned that I was rebooked in J (this was also the reason for my compliment email) and I suppose she can see that on my booking. I also suppose she can see that 5000 miles were added in CDG on my account as customer service compensation.
So overall, I am very impressed with the proactive and prompt response from AF, given this was a compliment email, and not the formal request for compensation. I haven't replied to the email yet, but I hesitate in adding - again - on the reply that I ended up in business on the CDG-HKG sector...