Those tables are often wrong. That can cause all sorts of issues and a big reason why Linux tends to have sleep issues and why windows modern standby exists. When that happens you're either maintaining workarounds on the kernel side or patching the acpi table yourself (terrifying, see this example [1]). The hope is that the end user will eventually apply firmware updates that might not exist for months or years. With device trees, the kernel applies a patch and it rolls out with the next update.
