I don't think it was a dumbing down move. Too many apps, especially games with large data downloads, are not written to take advantage of adoptable storage. Samsung is not the only one doing this, count LG, Sony, and etc in as well.
Making any mistake or trying to manipulate app's data locations can corrupt or ruin the entire Android/data folder in the internal storage which would make a large amount of apps installed broken or forced to reinstall data, leading in lost data. I know first hand as I experimented on a friend's Nvidia Shield. Too many apps are just stubborn at the moment.