Yeah this is a downside of the NTG6 Version of MBUX where as new EQA has NTG7 MBUX version.
I don't think the new EQA even for the lower spec cars get the option for the smaller display area like they do with the NTG6 Version. I think Mercedes developers were lazy and didn't want to code for the 2 different screen sizes so Apple Car Play will only be sized for the smaller screen size. (assume its the same for Android) You would think it wouldn't take much to modify the code and do an over the air update but I wouldn't hold my breath for it to change