5008 RPM drop while driving

Hello everyone. When I drive my 2022 model 5008 GT BlueHdi Eat8 on a flat road or down a hill, when I take my foot off the gas, the car is in gear but only idles. When I give it gas, the speed returns to normal, and when I take off the gas again, it drops to idle. I previously drove a 2020 3008 GTline BlueHdi Eat8 and it didn't have this problem. The authorized service says it's normal. Does anyone have any information? Does it idle while gliding in these models? Thanks in advance.

I also have a drop in rpm while driving. I'm a 2023 model 5008 user. I think this drop is related to the engine's carbon emissions. It's called the 'gear in neutral' mode. There's information in the user manual. It happens outside of sport mode. It's said to be automatic because it's a more economical drive.