I have a similar machine, same generation (Asus 1000H), dual booting with linux and Haiku Beta 5. When coldbooting Haiku, shutdown and restart work fine, but when booting Haiku after linux, shutdown doesn’t turn the machine off (have to use the power button to do it). My linux installation sets the HDD spin to always on, via hdparm.
These kind of errors are quite common, vendors create objects of wrong type and other errors. ACPICA is quite good at fixing or ignoring these kind of errors now, and somethings are only enabled if OS is windows.
It is more likely to be a hang in the shutdown, and in this case it may be the ‘shutdown should happen on boot processor’) problem as this was an older laptop than I understood before.