I actually MISS older android variants, as I could get root, and then change vold.fstab to mount and EXT3/4 partition on the SDCard as internal storage, and get around that bullshit straight up.
Google really does not want you to do that, because they are sycophantic ass lickers to the app makers, who want to keep the app's data "SUPER SECRET! USER NO TOUCHY!", which is why adopted storage is encrypted, and why the app developers *STILL* can demand that the app's private data hog the fuck out of internal storage. (Facebook, You are a whore about this. There is NO REASON for your demands. NONE. Especially when you want to gobble down 400mb of space JUST FOR YOURSELF.)
Throw into that how the handset makers always want to make the partitioning of the device's NAND/eMMC such that app storage is crippled on some damnably tiny 1gb volume, so they can claim "32gb of storage!!! WOW!!" on the /sdcard mounted area. In reality, the users would likely be MUUUUUUUUUUCH happier with a 16gb/16gb split, especially if the SDCard can be adopted.
(But then they couldn't hawk how you *NEEEEEEEEEEEEEEEEEEED* to update to the newest handset next christmas.)
Apps like Link2SD use root permissions to set up symbolic links (Since the internal storage partition the apps want to hog up is ext4 in nearly all phones, and support the feature) that point the app's private storage directory to another EXT4 volume (A special partition on the SDCard that gets mounted at boot). This lets the apps hog that space all they want, they only actually occupy 4kb (The EXT4 cluster allocation size) on the actual internal storage.
Google of course, did everything in its power to make that stop being easily done, and wont come out with some balls and tell the likes of Facebook to go pound sand, the user gets to specify where their goddamn app gets installed.