Goldorak
Thank you for the time educating me in the French savoir faire.
Personally I believe when a pledge has been made it needs to be fulfilled. A choice of hotels has been made on the premises of being an Accor four-star hotel, and charged accordingly. Either property and Accor deliver on what has been promised, agree to offer a proper compensation or it is a scam, a rip-off.
In the good old days... nobody would have been made aware. Nowadays either Accor and property offer a compensation for the no upgrades, insults and gross cleaning issues on two rooms or they are forced to come out, by their customers, who voice out loud and make sure others will not fall to the same scam. The OP may bear a loss, but ultimately, also according to your own remark of French way of vivre, I have been educated that in France I ought NOT to start choosing an Accor property, better choose Hilton or the best price offered in town. That simple.
When enough customers do it, either Accor rectifies the situation or their revenue may flow from different Geos.
PS - In Amsterdam, at a central location, Ibis Styles upgraded my room to a very nice view and I had a FULL bottle of wine with two glasses in my room waiting when I arrived; Checked in at 11am. There is something very wrong when Ibis Styles, that cost less, are better hoteliers than Mercure four star properties.